United, States
Environmental Protection
Agency
Office of Research and
Development
Washington, DC 20460
EPA/600/R-00/086
August 2000
http://www.epa.gov
Arsenic Removal from
Drinking Water by
Iron Removal Plants
As (111)
As(V)
F
fr
4*
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EPA/600/R-00/086
August 2000
Arsenic Removal from
Drinking Water by
Iron Removal Plants
by
Keith Fields
Abraham Chen
Lili Wang
Battelle
Columbus, OH 43201-2693
Contract No. 68-C7-0008
Work Assignment 3-09
for
Work Assignment Manager
Thomas J. Sorg
Water Supply and Water Resources Division
National Risk Management Research Laboratory
Cincinnati, OH 45268
National Risk Management Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268
Printed on Recycled Paper
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Disclaimer
The information in this document has been funded by the United States Environmental Protection
Agency (EPA) under Work Assignment (WA) 2-09 of Contract No. 68-C7-0008 to Battelle. It has
been subjected to the Agency's peer and administrative reviews and has been approved for
publication as an EPA document. Mention of trade names or commercial products does not con-
stitute an endorsement or recommendation for use.
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Foreword
The United States Environmental Protection Agency is charged by Congress with protecting the
Nation's land, air, and water resources. Under a mandate of national environmental laws, the
Agency strives to formulate and implement action leading to a compatible balance between
human activities and the ability of natural systems to support and nurture life. To meet this man-
date, EPA's research program is providing data and technical support for solving environmental
problems today and building a science knowledge base necessary to manage our ecological
resources wisely, understand how pollutants affect our health, and prevent or reduce environ-
mental risks in the future. .
The National Risk Management Research Laboratory is the Agency's center for investigation of
technological and management approaches for reducing risks from threats to human health and
the environment. The focus of the Laboratory's research program is on methods for prevention
and control of pollution to air, land, water, and subsurface resources: protection of water quality in
public water systems; remediation of .contaminated sites and ground water; and prevention and
control of indoor air. The goal of this research effort is to evaluate the performance on a full-scale
level of five processes, including coagulation/filtration, lime softening, iron oxidation/filtration, ion
exchange, and activated alumina, to consistently remove arsenic over a sustained period of time
(1 year).
This publication has been produced as part of the Laboratory's strategic long-term research plan.
It is published and made available by EPA's Office of Research and Development to assist the
user community and to link researchers with their clients.
E. Timothy Oppelt, Director
National Risk Management Research Laboratory
in
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Abstract
This report documents treatment plant information as well as results of sampling and analysis at
two iron removal plants (referred to as Plants A and B). The objective of sampling and analysis
was to evaluate the effectiveness of the water treatment plants to consistently remove arsenic
(As) from source water. Additionally, data were collected in this study to evaluate the chemical
characteristics of residuals produced by the treatment processes.
The study was divided into three phases: source water sampling, preliminary sampling, and long-
term evaluation. The first phase, source water sampling, was conducted to evaluate source water
characteristics at each plant. The second phase, preliminary sampling, was initiated at Plant A in
April 1998 and at Plant B in May 1998. This phase consisted of a four-week sampling period to
refine procedures for subsequent events during the third phase. The third phase, long-term
evaluation, consisted of weekly sample collection and analysis beginning in June 1998 and
continuing through June 1999 at Plant A and through December 1998 at Plant B. Plant personnel
conducted all sampling during the long-term evaluation phase and Battelle coordinated sampling
logistics. Sludge samples also were collected at Plant A during a single sampling event from an
outdoor settling pond in November 1998. Samples of supernatant discharge (Plant A) and recycle
supernatant (Plant B) were collected monthly beginning in November 1998 and continuing until
June 1999 at Plant A and until January 1999 at Plant B.
Results from the long-term evaluation phase were varied regarding the ability of the iron removal
process to consistently achieve low-level arsenic concentrations (e.g., <5 ug/L in the finished
water). The total arsenic concentrations at Plant A were reduced by an average of 87%, which
represents a decrease in average arsenic concentration from 20.3 ug/L to 3.0 ug/L Adsorption
and coprecipitation with iron hydroxide precipitates are believed to be the primary arsenic removal
mechanisms. The total arsenic concentrations at Plant B were reduced by an average of 74%,
which represents a decrease in average arsenic concentration from 48.5 ug/L to 11.9 ug/L. At
Plant B, it appeared that only the paniculate arsenic in the source water was removed. This par-
ticulate arsenic was most likely associated with the oxidized iron particles present in the source
water (i.e., arsenic sorbed onto iron particles). The primary difference in arsenic removal efficiency
at Plants A and B is believed to be the amount of iron in the source water. Source water at Plant A
averaged 2,284 ug/L of iron, while Plant B averaged 1,137 ug/L. Increasing the iron in the source
water at Plant B using a coagulant, such as ferric chloride, would likely enable Plant B to consist-
ently achieve lower levels of arsenic.
None of the sludge samples collected at Plant A qualified as a hazardous waste based on the
Toxicity Characteristic Leaching Procedure (TCLP) test for metals. Therefore, nonhazardous waste
landfills should be able to accept the sludge generated by this treatment facility. Stricter hazard-
ous waste classification regulations in some states, such as California, on total arsenic concen-
trations in solid waste also were met at Plant A. Sludge samples were not collected at Plant B;
however, analytical results were provided from a 1994 sludge sampling event.
IV
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Contents
Foreword iii
Abstract '. iv
Figures , vii
Tables viii
Acronyms and Abbreviations ix
1.0 Introduction 1
1.1 Background 1
1.1.1 General Chemistry of Arsenic 1
1.1.2 Determination of Arsenic Species 3
1.1.3 Treatment Technologies for Arsenic Removal 3
1.1.4 Data Gaps 4
1.2 Objectives 4
1.3 Report Organization 4
2.0 Conclusions 5
3.0 Materials and Methods 6
3.1 General Project Approach 6
3.2 Preparation of Sampling Kits and Sample Coolers 7
3.2.1 Preparation of Arsenic Speciation Kits 7
3.2.2 Preparation of Recycle Backwash Water/Supernatant
Discharge Sampling Kits 8
3.2.3 Preparation of Sample Coolers 8
3.3 Sampling Procedures 9
3.3.1 General Approach and Sampling Schedules 9
3.3.2 Arsenic Field Speciation Procedure 10
3.3.3 Recycle Supernatant/Supernatant Discharge Sampling
Procedure 13
3.3.4 Sampling Procedure for Other Water Quality Parameters 13
3.4 Analytical Procedures 13
4.0 Results and Discussion 16
4.1 Plant Selection 16
4.2 Plant A 16
4.2.1 Plant A Description 17
4.2.2 Initial Source Water Sampling 17
4.2.3 Preliminary Sampling 17
4.2.4 Long-Term Sampling 22
4.2.4.1 Arsenic 22
4.2.4.2 Other Water Quality Parameters 24
4.2.4.3 Supernatant Discharge 24
4.2.4.4 Sludge 26
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4.3 PlantB 28
4.3.1 Plant B Description 28
4.3.2 Initial Source Water Sampling 28
4.3.3 Preliminary Sampling 30
4.3.4 Long-Term Sampling 33
4.3.4.1 Arsenic 33
4.3.4.2 Other Water Quality Parameters 34
4.3.4.3 Recycle Supernatant 37
4.3.4.4 Sludge 37
5.0 Quality Assurance/Quality Control 39
5.1 Quality Assurance Objectives 39
5.2 Overall Assessment of Data Quality 39
5.2.1 Total Arsenic, Aluminum, Iron, and Manganese 39
5.2.2 Water Quality Parameters 40
5.2.3 TCLP Metals in Sludge 40
6.0 References 41
Appendices
Appendix A: Complete Analytical Results from Long-Term Sampling at Plant A 43
Appendix B: Complete Analytical Results from Long-Term Sampling at Plant B..'... 57
VI
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Figures
Page
Figure 1-1. Solubility Diagrams for As(lll) and As(V) 2
Figure 3-1. Example of Sample Bottle Label 9
Figure 3-2. Photographs of a Typical Sample Cooler (with Three Sample
Compartments) and a Color-Coded Instruction Sheet 11
Figure 3-3. Instruction Sheet for Arsenic Field Speciation 12
Figure 3-4. Instruction Sheet for Recycle Supernatant/Supernatant Discharge
Sampling 14
Figure 4-1. Schematic Diagram, Plant A 18
Figure 4-2. Process Flow Diagram and Sampling Locations at Plant A 20
Figure 4-3. Total Arsenic Analytical Results During Long-Term Sampling at
Plant A 23
Figure 4-4. Arsenic Form and Species Analytical Results During Long-Term
Sampling at Plant A 25
Figure 4-5. Inlet Turbidity, pH, Hardness, and Alkalinity Analytical Results at
Plant A 27
Figure 4-6. . Schematic Diagram, Plant B 29
Figure 4-7. Process Flow Diagram and Sampling Locations at Plant B 31
Figure 4-8. Total Arsenic Analytical Results During Long-Term Sampling at
Plant B 34
Figure 4-9. Arsenic Form and Species Analytical Results During Long-Term
Sampling at Plant B 35
Figure 4-10. Inlet Turbidity, pH, Hardness, and Alkalinity Analytical Results at
PlantB 37
VII
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Tables
Page
Table 3-1. Sample Containers and Preservation Methods 8
Table 3-2. Summary of Sampling Activities at Plants A and B 10
Table 3-3. Summary of Sampling Schedule for Plants A and B 10
Table 3-4. Summary of Analytical Methods for Arsenic Treatment Study 15
Table 4-1. Initial List of Treatment Facilities Identified for the Study 16
Table 4-2. Source Water Analytical Results at Plant A (February 10,1998) 19
Table 4-3. Analytical Results from Preliminary Sampling at Plant A (April 22 to
May 13, 1998) 21
Table 4-4. Summary of Arsenic Analytical Results at Plant A 22
Table 4-5. Summary of Water Quality Parameter Analytical Results at Plant A.. 26
Table 4-6. Summary of Analytical Results from Supernatant Discharge
Samples at Plant A 27
Table 4-7. Analytical Results of Sludge Sampling at Plant A 28
Table 4-8. Source Water Analytical Results at Plant B (February 4,1998) 30
Table 4-9. Analytical Results from Preliminary Sampling at Plant B (May 7
through May 28, 1998) 32
Table 4-10. Summary of Arsenic Analytical Results at Plant B 33
Table 4-11. Summary of Water Quality Parameter Analytical Results at Plant B.. 36
Table 4-12. Summary of Analytical Results from Recycle Supernatant Samples
at Plants 38
VIII
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Acronyms and Abbreviations
AF after filtration
As arsenic
AS after softening
ASTM American Society for Testing and Materials
, AWWA American Water Works Association
AWWARF American Water Works Association Research Foundation
cfs cubic feet per second
Dl distilled
EDR electrodialysis reversal
EPA United States Environmental Protection Agency
GFAAS graphite-furnace atomic-absorption spectrophotometer
Gl gastrointestinal
gpm gallons per minute
GW ground water
HCI hydrochloric acid
HOPE high-density polyethylene
ICP-MS inductively coupled plasma/mass spectrometry
ID identification
IN inlet
KMnO4 potassium permanganate
MCL maximum contaminant level
MDL method detection limit
mgd million gallons per day
MS matrix spike
MSD matrix spike duplicate
ND not detected
NOM natural organic matter
NS not sampled
NTU nephelometric turbidity units
PF prefiltration
POC point of contact
ppm parts per million
psi pounds per square inch
IX
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QA
QAPP
QA/QC
RPD
SDWA
SW
TCLP
TDS
TOG
TSS
WA
WAM
quality assurance
Quality Assurance Project Plan
Quality Assurance/Quality Control
relative percent difference
Safe Drinking Water Act
surface water
Toxicity Characteristic Leaching Procedure
total dissolved solids
total organic carbon
total suspended solids
work assignment
work assignment manager
%R
percent recovery
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Acknowledgments
Sincere appreciation is extended to the two water treatment facilities that participated in this study.
The staff from each facility contributed greatly to this project by collecting samples every week for
more than 12 months at Plant A and more than 6 months at Plant B. Their work on this project
was uncompensated, making their superb efforts even more remarkable. Personnel from both
plants are thanked for their hard work and dedication throughout the duration of this project.
XI
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1.0 Introduction
This project consists, in part, of a field study to collect
drinking water samples from various locations through-
out the treatment processes at two iron removal plants.
These samples were analyzed and used to evaluate the
effectiveness of conventional iron removal processes to
consistently reduce arsenic (As) in source water to low
levels. This project also includes the collection of pro-
cess residual samples that were used to determine the
quantity and chemical characteristics of the residuals pro-
duced by the treatment processes. This report describes
the design and operation of the two treatment plants and
presents the analytical results of the water samples col-
lected during the study.
1.1 Background
The Safe Drinking Water Act (SDWA) of 1974 mandates
that the United States Environmental Protection Agency
(EPA) identify and regulate drinking water contaminants
that may have an adverse human health effect and that
are known or anticipated to occur in public water supply
systems. Arsenic is a naturally occurring contaminant
that has known adverse human health effects. Excessive
amounts of arsenic can cause acute gastrointestinal (Gl)
and cardiac damage. Chronic doses can cause vascular
disorders such as blackfoot disease (Chen et al., 1994),
and epidemiological studies have linked arsenic to skin
and lung cancer (Tate and Arnold, 1990). In 1975, under
the SDWA, EPA established a maximum contaminant
level (MCL) for arsenic at 0.05 mg/L. Since that time, revi-
sion of the MCL has been considered a number of times,
but no change has been made. The SDWA was amended
in 1996, and these amendments required that the EPA
develop an arsenic research strategy and publish a pro-
posal to revise the arsenic MCL by January 2000.
A draft arsenic research plan was prepared by the EPA
in December 1996 and was finalized in February 1998
based upon a technical review by the EPA's Board of
Scientific Counselors (EPA, 1998). The plan identifies the
research needed by the EPA to support a proposed revi-
sion of the arsenic MCL. The plan also identifies a num-
ber of treatment methods available for arsenic removal
and recognizes the need to determine the capability of
these technologies to remove arsenic to a level signifi-
cantly lower than the current MCL. This study was con-
ducted as part of an EPA Work Assignment (WA) to
determine the ability of conventional water treatment pro-
cesses to consistently remove arsenic from drinking water.
1.1.1 General Chemistry of Arsenic
Arsenic is a common, naturally occurring drinking water
contaminant that originates from arsenic-containing rocks
and soil and is transported to natural waters through
erosion and dissolution. Arsenic occurs in natural waters
in both organic and inorganic forms. However, inorganic
arsenic is predominant in natural waters and is the most
likely form of arsenic to exist at concentrations that cause
regulatory concern (Edwards et al., 1998).
The valence and species of inorganic arsenic are de-
pendent on the oxidation-reduction conditions and the
pH of the water. As a general rule of thumb, the reduced,
trivalent from [As(lll)] normally is found in ground water
(assuming anaerobic conditions) and the oxidized, pen-
tavalent form [As(V)] is found in surface water (assuming
aerobic conditions), although this rule does not always
hold true for ground water, where both forms have been
found together in the same water source. Arsenate
exists in four forms in aqueous solution based on pH:
H3AsO4, H2AsO4~, HAsO42~, and AsO^. Similarly, arsenite
exists in five forms: H4AsO3+, H3AsO3, H2AsO3", HAsO32",
and AsOg3". As shown in Figure 1-1, which contains solu-
bility diagrams for As(lll) and As(V), ionic forms of arsen-
ate dominate at pH >3, and arsenite is neutral at pH <9
and ionic at pH >9. Conventional treatment technologies
used for arsenic removal, such as iron removal, rely on
adsorption and coprecipitation of arsenic to metal hydrox-
ides. Therefore, the valence and species of soluble arse-
nic are very significant in evaluating arsenic removal.
Although soluble arsenic species typically make up the
majority of the total arsenic concentration in natural
waters, some research indicates that arsenic can exist as
particulate at significant concentrations. Studies by Cheng
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.1
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Figure 1-1. Solubility Diagrams for As(lll) and As(V)
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et al. (1994) and Hemond (1995) measured particulate
arsenic at levels of 17 and 50% of the total arsenic con-
centration, respectively, in subject source waters. There-
fore, determination of the particulate arsenic concentration
is important because it can provide insight into the arse-
nic removal mechanisms that occur during treatment.
1.1.2 Determination of Arsenic Species
Although total arsenic can be effectively preserved in
field samples, presently no method exists to consistently
preserve inorganic arsenic species in field samples.
Preservation of total arsenic is accomplished by acidi-
fying the sample to pH <2 in the field. However, a high
level of ambiguity exists when acids such as nitric acid
(HNO3) or hydrochloric acid (HCI) are used to preserve
inorganic species of arsenic. Interconversion of As(lll)
and As(V) in samples preserved with 0.05 N HCI have
been reported to occur within one day (Andreae, 1977).
Another laboratory study conducted by Eaton et al.
(1997) examined preservation of arsenic using humic
acid, ascorbic acid, and HCI; the study concluded that no
effective method exists for preserving As(lll) and As(V)
in water samples. Some researchers have used freezing
of samples as a means of preserving the inorganic spe-
cies of arsenic. However, freezing is neither a cost-
effective nor a practical method for field sampling.
In response to the lack of techniques available for ade-
quately preserving arsenic species, field speciation pro-
tocols have been developed by Ficklin (1982), Clifford et
al. (1983), and Edwards et al. (1998). In each of these
studies, an anion exchange resin column is used for field
speciation of arsenic. Ficklin (1982) used a strong anion
exchange resin (Dowex 1x8, 100-200 mesh, acetate
form) in a 10 cm x 7 mm glass column to separate
As(lll) from As(V) in water samples that had been filtered
through a 0.45-um membrane filter and acidified with 1%
HCI. The resin was supplied in chloride form and was
converted to the acetate form. However, in the protocol by
Clifford et al. (1983), a chloride-form strong base anion
resin (ASB-2, 30-60 mesh) was used to separate As(lll)
from As(V). In this method, the sample was not filtered
or preserved with acid. Both Ficklin and Clifford used a
graphite-furnace atomic-absorption spectrophotometer
(GFAAS) to determine the arsenic concentration.
More recently, Edwards et al. (1998) made the following
modifications to Ficklin's method: (1) Substituted 50-100
mesh resin for the 100-200 mesh resin to allow faster
sample flow. (2) Used 12 cm x 15 mm polypropylene col-
umns to improve safety and speed of sample treatment.
(3) Used 0.05% H2SO4 instead of 1% HCI to acidify
samples prior to resin treatment. Edwards et al.'s use of
H2SO4 helped to prevent potential problems associated
with overacidification of the sample, and also helped to
prevent Cl~ from interfering with the inductively coupled
plasma/mass spectrometry (IGP-MS) analysis. The re-
ported recoveries of As(III) and As(V) ranged from 80 to
120% by Ficklin (1982), 95 to 117% by Clifford et al.
(1983), and 100 to 105% by Edwards et al. (1998). For
this study, the decision was made to utilize a field speci-
ation technique similar to that used by Edwards et al.
(1998).
1.1.3 Treatment Technologies for
Arsenic Removal
Several common treatment technologies are used for the
removal of inorganic contaminants, including arsenic, from
drinking water supplies. Large-scale treatment facilities
often use conventional coagulation with alum or iron salts
followed by filtration to remove arsenic. Chemical precipi-
tation is another common, conventional treatment process
used for water softening as well as iron and manganese
removal that can potentially remove arsenic from source
waters. Smaller-scale systems and point-of-entry systems
often use anion exchange resins or activated alumina.
Other arsenic removal technologies include manganese
greensand, reverse osmosis, electrodialysis reversal
(EDR), nanofiltration, and adsorption on activated carbon.
This, report focuses on iron removal, a conventional treat-
ment process used for arsenic removal at large-scale
operations. Two additional reports have been developed
for (1) coagulation/filtration and lime softening plants and
(2) anion exchange and activated alumina plants.
Chemical precipitation/filtration commonly is used for re-
moval of iron from source waters. This process, referred
to in this document as iron removal, involves two major
steps: (1) oxidation of reduced iron, Fe(II), to the rela-
tively insoluble Fe(lll) in order to form precipitates; and
(2) filtration of the water to remove the precipitated iron
hydroxides. The most common oxidants used to precipi-
tate soluble iron are air, chlorine, and potassium per-
manganate.
Iron removal can be used to remove arsenic from drink-
ing water. Two primary removal mechanisms exist: ad-
sorption and coprecipitation (Benefield and Morgan,
1990). During the adsorption process, dissolved arsenic
attaches to the surface of a particle or precipitate. And
during the coprecipitation process, dissolved arsenic is
adsorbed to a particle and entrapped as the particle con-
tinues to agglomerate. The following major steps occur
when using iron removal for arsenic treatment: (1) the sol-
uble iron and any As(lll) are oxidized; (2) As(V) attaches
to the iron hydroxides through adsorption and/or coprecip-
itation; and (3) the particle/precipitate subsequently is fil-
tered from the water.
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Several bench- and pilot-scale studies and some short-
term full-scale evaluations have been conducted to eval-
uate arsenic removal during iron hydroxide precipitation.
Most of the studies have focused on removal of As(V)
rather than As(lll) because better As(V) removal can be
achieved under comparable conditions and As(lll) can
be easily converted to As(V) using a strong oxidant such
as chlorine (Hering et al., 1996; Sorg, 1993). McNeill and
Edwards (1995) conducted a survey of full-scale treat-
ment facilities and observed that arsenic removal effi-
ciencies of 80 to 95 percent were obtained at facilities
with greater than 1.5 mg/L Fe(ll) in the source water.
However, arsenic removal efficiency may be reduced in
the presence of orthophosphate, natural organic matter
(NOM), and silicate due to competition for sorptive sites
on iron hydroxide precipitates (Edwards, 1994; Meng et
al., 2000).
Previous studies also indicate that arsenic removal dur-
ing iron hydroxide precipitation is directly correlated with
the initial, or inlet, iron concentration (i.e., arsenic re-
moval efficiency increases with increasing iron concen-
trations) (Sorg and Logsdon, 1978; Sorg, 1993; Hering
et al., 1996; Gulledge and O'Conner, 1973). Also, arse-
nic removal efficiency appears to be independent of ini-
tial arsenic concentration at levels of interest to drinking
water treatment (Hering et al., 1996; Cheng et al., 1994;
Edwards, 1994). Other research indicates that As(V)
removal is not pH-dependent between pH 5.5 and 8.5 for
iron hydroxide precipitation (Sorg and Logsdon, 1978;
Sorg, 1993; Hering et al., 1996).
1.1.4 Data Gaps
The removal of arsenic from drinking water by adsorp-
tion and coprecipitation with metal hydroxides has been
extensively studied at the laboratory and pilot-scale level.
Although some short-term full-scale evaluations have
been performed for iron removal, little data exist on the
capability of (natural) iron removal in full-scale applica-
tions to reduce arsenic on a sustained basis. Thus, a
need exists to determine the effectiveness of the iron
removal process to produce drinking water with low lev-
els of arsenic on a long-term basis, under varying opera-
tional and seasonal conditions.
Another data gap is the generation and disposal of resid-
uals from conventional drinking water treatment proces-
ses. Currently, little or no data exist on the amounts and
the chemical composition of residuals generated by the
arsenic removal processes and the environmental impacts
of their disposal. Therefore, information needs to be col-
lected on the quantity and the chemical characteristics of
the wastes produced by iron removal plants.
1.2 Objectives
One objective of this study was to evaluate the effective-
ness of conventional iron removal to consistently reduce
arsenic concentrations in source water to low levels.
This report presents the results of weekly monitoring for
approximately one year and 6 months at Plants A and B,
respectively.
Another objective of this study was to examine the resid-
uals""produced during treatment at iron removal plants.
Information was collected on the chemical characteristics
of the wastes produced by these drinking water treatment
processes.
1.3 Report Organization
Section 1.0 provides background information for the field
study and project objectives. Section 2.0 of this report
presents the conclusions from the study of the two iron
removal plants. Section 3.0 describes the materials and
methods used to conduct this study. Section 4.0 dis-
cusses the results of the study and Section 5.0 provides
specific information on quality assurance/quality control
(QA/QC) procedures. Section 6.0 is a list of references
cited in the text. Appendices A and B present the com-
plete set of analytical data collected at Plants A and B,
respectively, during long-term sampling.
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2.0 Conclusions
The U.S. EPA has begun the process of revising the
arsenic MCL. It is anticipated that the revised limit will be
significantly lower than the current MCL of 0.05 mg/L.
Therefore, there is a need to determine the ability of exist-
ing treatment processes to consistently remove arsenic
to low levels. The primary objectives of this study were to
document arsenic removal at two iron removal plants,
and to assess potential impacts of residuals (sludge and
supernatant water) at these treatment plants.
The study was divided into three major phases: source
water sampling (February 1998), preliminary sampling
(April and May 1998), and long-term sampling (June
1998 through June 1999). For the first phase, Battelle
staff traveled to each facility to conduct source water
sampling, which provided information on source water
characteristics. The second phase, preliminary sampling,
consisted of a four-week sampling period to refine the
sampling approach before implementing the long-term
sampling phase. Battelle staff again traveled to each
facility to coordinate the first sampling event and train
plant personnel in sampling procedures for subsequent
events. The third phase, long-term evaluation, consisted
of weekly collection and analysis of water samples at both
water treatment plants. The long-term evaluation also
included sludge sampling (November 1998 at Plant A
only), supernatant discharge sampling (November 1998
through June 1999 at Plant A), and recycle supernatant
sampling (November 1998 through January 1999 at
Plant B). During the long-term sampling, plant personnel
conducted sampling and Battelle coordinated sampling
logistics.
The primary focus of this study was the long-term per-
formance of the two iron removal plants. Total arsenic
concentrations at Plant A were reduced from an average
of 20.3 ug/L to 3.0 ug/L. Total arsenic concentrations at
Plant B were reduced from an average of 48.5 ug/L to
11.9 ug/L. Adsorption and coprecipitation of As(V) with
iron hydroxides precipitates are believed to be the pri-
mary arsenic removal mechanism at Plant A. Plant A
oxidized As(lll) in the source water to As(V) using chlori-
nation. At Plant B, it appeared that only the particulate
arsenic in the source water was removed. Particulate
arsenic most likely represents the arsenic sorbed to oxi-
dized iron particles. The primary difference in arsenic
removal between Plants A and B is believed to be the
amount of iron in the source water. Source water at
Plant A averaged 2,284 ug/L of iron, while Plant B aver-
aged 1,137 ug/L. Therefore, increasing the available iron
at Plant B by using a coagulant such as ferric chloride
would likely enable Plant B to consistently achieve lower
levels of arsenic.
The secondary focus of this study was on the chemical
characteristics of the residuals generated during the treat-
ment processes. None of the sludge samples collected at
Plant A qualified as a hazardous waste based on Tox-
icity Characteristic Leaching Procedure (TCLP) tests for
metals. Therefore, sludge generated by this plant should
be accepted by nonhazardous waste landfills. Sludge
samples were not collected at Plant B; however, the plant
did provide analytical results from a 1994 sampling event.
TCLP tests were not performed on this sample, although
the total arsenic concentration exceeded stricter require-
ments in California regarding hazardous waste classifica-
tion. Supernatant water from the settling pond at Plant A
was discharged to the sanitary sewer, whereas backwash
water at Plant B was allowed to settle in a concrete vat
then combined with the source water. The recycle super-
natant at Plant B did not appear to adversely impact treat-
ment plant operations.
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3.0 Materials and Methods
This section discusses the materials and methods used
for performing the source water, preliminary, and long-
term sampling and data collection at two iron removal
plants. Section 3.1 describes the general project ap-
proach. Section 3.2 describes the preparation of arsenic
speciation kits and sample coolers. Section 3.3 provides
detailed sampling procedures. Section 3.4 discusses per-
tinent analytical procedures.
3.1 General Project Approach
Several consecutive tasks were performed to accomplish
the study objectives described in Section 1.2. These tasks
involved the following activities:
• Select treatment plants and conduct an initial site
visit to collect source water samples at each
selected plant
• Prepare a preliminary sampling and data collection
plan for each plant
• Finalize the sampling and data collection plan after
completion of four weekly preliminary sampling
events at each plant
• Implement the final sampling and data collection
plan with weekly sampling events at each plant for
up to one year.
For initial plant selection, a list of potential treatment
plant candidates was compiled. Plant operators or other
key personnel were contacted via telephone to obtain/
confirm information and solicit interest in participating in
the project. Each facility was evaluated on the following
criteria: source water arsenic concentrations, source
water type, available manpower to conduct the year-long
study, availability of historical arsenic data, and plant
size. Battelle recommended the selection of two iron
removal plants (designated as Plants A and B) for initial
site visits and source water sampling. These recommen-
dations were later approved by the EPA Work Assign-
ment Manager (WAM). The information collected during
the site visits, including the concentration and speciation
of arsenic in each source water, was tabulated and used
as the basis for the final plant selection.
Following the final plant selection (Plants A and B were
selected), a preliminary sampling and data collection plan
was prepared for each plant to document the plant's oper-
ation and performance for arsenic removal and the cri-
tical parameters that would impact the removal. Each
preliminary plan also described the data collection effort
to characterize the residuals produced by the treatment
process. The approved preliminary plans were imple-
mented at both plants over a four-week trial period. A
Battelle staff member revisited the plants during the first
week of the trial period to observe plant operations, per-
form sampling, conduct training of plant support per-
sonnel, and establish/coordinate all required logistics
(such as receiving/shipping of sample coolers, chain-of-
custody coordination, communication methods, and emer-
gency/contingency plans). The remaining three sampling
events during the preliminary sampling were performed
by a designated point of contact (POC) or an alternate at
each plant. The experience gained during the trial period
was used to finalize the long-term sampling and data
collection plans.
All water and residual samples were collected and ana-
lyzed in accordance with the Category III Quality Assur-
ance Project Plan (QAPP) prepared by Battelle (1998)
for this project. Water samples were collected weekly
from four sampling locations at Plant A: (1) the inlet to
the treatment plant (IN); (2) before the filtration process
(prefiltration [PF]); (3) after the Nitration process (AF);
and (4) after a final zeolite resin softening process (AS).
Also, water samples were collected weekly from three
sampling locations at Plant B: (1) the inlet to the treatment
plant (IN); (2) before the filtration process (PF); (3) and
after the filtration process at the plant outlet (AF). During
the preliminary and long-term sampling phases, field arse-
nic speciation sampling was conducted once every four
weeks. Starting from November 1998, samples of super-
natant discharge (from a settling pond at Plant A) or recy-
cle supernatant (from a concrete vat at Plant B) were
collected once every four weeks from each plant. Finally,
-------
three sludge samples were collected from the settling
pond at Plant A during one sampling event.
All sample containers and arsenic speciation kits were
prepared and sent in coolers on a weekly basis to each
plant via Federal Express. The coolers were returned to
Battelle immediately after the sample collection had been
completed. Analyses of arsenic, aluminum, iron, and
manganese in water were conducted by Battelle using
an ICP-MS method. Wilson Environmental Laboratories
in Westerville, OH, was subcontracted to perform all
other chemical analyses. Battelle coordinated all sam-
pling logistics.
3.2 Preparation of Sampling Kits
and Sample Coolers
All arsenic speciation kits, recycle supernatant/superna-
tant discharge sampling kits, and sample coolers were
prepared at Battelle. The following sections describe the
relevant preparation procedures.
3.2.1 Preparation of Arsenic
Speciation Kits
The arsenic field speciation method used an anion ex-
change resin column to separate the soluble arsenic
species, As(V) and As(lll). A 250-mL bottle (identified as
bottle A) was used to contain an unfiltered sample,
which was analyzed to determine the total arsenic con-
centration (both soluble and particulate). The soluble
portion of the sample was obtained by passing the unfil-
tered sample through a 0.45-um screw-on disc filter to
remove any particulate arsenic and collecting the filtrate
in a 125-mL bottle (identified as bottle B). Bottle B con-
tained 0.05% (volume/volume) ultra-pure sulfuric acid to
acidify the sample to about pH 2. At this pH, As(lll) was
completely protonated as H3AsO3, and As(V) was pres-
ent in both ionic (i.e., H2AsO4~) and protonated forms
(i.e., H3AsO4) (see Figure 1-1). A portion of the acidified
sample in bottle B was run through the resin column.
The resin retained the As(V) and allowed As(lll) (i.e.,
H?AsO3) to pass through the column. (Note that the resin
will retain only H2AsO4~ and that H3AsO4, when passing
though the column, will be ionized to H2AsO4~ due to
elevated pH values in the column caused by the buffer
capacity of acetate exchanged from the resin.) The elu-
ate from the column was collected in another 125-mL
bottle (identified as bottle C). Samples in bottles A, B,
and C were analyzed for total arsenic using ICP-MS.
As(lll) concentration made up the total arsenic concen-
tration of the resin-treated sample in bottle C. The As(V)
concentration was calculated by subtracting As(lll) from
the total soluble arsenic concentration of the sample in
bottle B.
Arsenic speciation kits were prepared in batch at Battelle
based on a method modified from Edwards et al. (1998).
Each arsenic speciation kit contained the following:
• One anion exchange resin column
• Primary and duplicate A, B, and C bottles
• One 400-mL disposable beaker
• Two 60-mL disposable syringes
• .Several 0.45-um syringe-adapted disc filters.
Each speciation kit was packed in a plastic zip lock bag
along with latex gloves and a step-by-step speciation
sampling instruction sheet. All chemicals used for pre-
paring the kits were of analytical grade or higher. The
arsenic speciation kits were prepared according to the
following procedures:
• Resin Preparation. Before packing into columns,
the anion exchange resin (Dowex 1-X8, 50-100
mesh) was converted from the chloride form (as
supplied by Supelco) to the acetate form according
to the method used by Edwards et al. (1998). First,
1 kg of the resin was placed in a 3-L beaker. One
liter of 1N sodium hydroxide (NaOH) then was
added to the resin, stirred for an hour using an
overhead stirrer, and drained. This NaOH rinse
was repeated sequentially for three times. The
NaOH-treated resin was then rinsed with two 1 -L
batches of reagent grade water, followed by three
acetic acid rinses. Each acetic acid rinse consisted
of adding 1 L of 1N reagent grade acetic acid to
the resin, stirring for 5 minutes, and draining the
spent acid. The acetic acid-treated resin was
subsequently rinsed with 3-L batches of reagent-
grade water. The resin slurry was stored in a 2-L
bottle and kept moist until use.
• Anion Exchange Column Preparation. The resin
columns used were 12 cm x 15 mm in size and
made of polypropylene (Bio-Rad Laboratories,
CA). Each column was slurry packed with about
20 g (drained weight) of the prepared resin,
yielding a resin depth of approximately 10.5 cm.
The column was sealed with two plastic caps (one
each on top and bottom) to prevent contamination
and retain moisture prior to use.
• Sample Bottles. VWRbrand™ TraceClean™ high-
density polyethylene (HOPE) sample bottles (250
and 125 mL) were used to prepare bottles A, B,
and C. Bottles A and C were spiked with 500 and
250 uL, respectively, of concentrated ultra-pure
HNO3; and bottle B was spiked with 1.25 mL of 5%
(volume/volume) ultra-pure sulfuric acid (H2SO4).
H2SO4 was used to acidify the sample in bottle B
because CI" in HCI could interfere with the ICP-MS
arsenic detection and HNO3 (an oxidizing agent)
-------
could damage the resin or form nitric acid-arsenic
redox couples (Edwards et al., 1998).
• Beaker, Syringes, and Filters. One 400-mL
disposable plastic beaker was used to collect a
water sample. Samples were filtered using 60-mL
disposable plastic syringes with 0.45-um scre'w-on
disc filters. All disposable beakers, syringes, and
filters were rinsed with distilled (Dl) water and air-
dried before being packed into the sampling kits.
3.2.2 Preparation of Recycle Backwash
Water/Supernatant Discharge
Sampling Kits
The recycle backwash water/supernatant discharge sam-
ples were collected for pH, total and soluble As, Al, Fe,
and Mn measurements. Each sampling kit contained the
following items:
• Primary and duplicate A and B bottles (both
preserved with HNO3) to contain unfiltered and
filtered samples for total and soluble As, Al, Fe,
and Mn analyses
• One 400-mL disposable beaker
• Two 60-mL disposable syringes
• Several 0.45-um screw-on disc filters
• Bottles provided by Wilson Environmental
Laboratories used for pH analyses.
The sampling kit was prepared in a similar way as the ar-
senic speciation kit except that bottle B was preserved
with HNO3 instead of H2SO4. The sampling kit was packed
in a plastic zip lock bag along with latex gloves and a
step-by-step sampling instruction sheet.
3.2.3 Preparation of Sample Coolers
Sample containers for analysis of all water quality param-
eters except for total As, Al, Fe, and Mn were provided by
Wilson Environmental Laboratories. These containers
were new, rinsed with Dl water, allowed to air dry, and
contained appropriate preservatives before being deliv-
ered to Battelle. These bottles were labeled with the letter
D, E, F, or G, designating the specific analysis to be per-
formed. Table 3-1 lists the sample container size and type
Table 3-1. Sample Containers and Preservation Methods
Container Size Container Type
Arsenic Speciation Samples
ocn mi /A\ certified clean HOPE
250 mL (A) bottles
.,„,. . /m certified clean HOPE
125 mL (B) bott|eg
•ioc.v,i /r>\ certified clean HOPE
125mL(C) bott|es
Preservation Method
4°C
HNO3 for pH <2
4°C
0.05 % H2SO4
4°C
HNO3 for pH <2
Analyte
Total As, Al, Fe, Mn
Dissolved As, Al, Fe, Mn
Dissolved As, Al, Fe, Mn
Hold Time
6 months
6 months
6 months
Recycle Backwash Water/Supernatant Discharge Samples
250 mL (D) plastic
„.. . ... certified clean HOPE
250 ml (A) bott,es
osnmi /m certified clean HOPE
250mL(B) bottles
Water Quality Parameter Samples.
250 mL (D) plastic
250 mL (D) plastic
250 mL (E) plastic
250 mL (F) plastic
500 mL (G) glass
Sludge Samples
8oz(SL1) glass jar
4 oz (SL2) glass jar
4 oz (SL2) glass jar
4°C
4°C
HNO3 for pH <2
4°C
HNO3 for pH <2
4°C
4°C
4°C
HNO3 for pH<2
4°C
Ha SO4 for pH <2
4°C
H2SO4 for pH<2
4°C
4°C
4°C
PH
Total As, Al, Fe, Mn
Dissolved As, Al, Fe, Mn
Alkalinity
PH
Turbidity
Sulfate
Hardness
NO3VNO2-
TOC
Total As, Al, Fe, Mn
Water content, pH,
TCLP metals
Water content, pH,
TCLP metals
immediate
6 months
6 months
14 days
immediate
48 hours
28 days
6 months
28 days
14 days
6 months
14 days
14 days
TOC = total organic carbon.
TSS s total suspended solids.
-------
(for water and sludge samples), sample preservation used,
analysis to be performed, and holding time. All sample
containers were labeled prior to shipment.
Figure 3-1 presents an example sample bottle label. The
sample identification (ID) consisted of five parts, includ-
ing a two-letter code for a water treatment plant, the
sampling date (mm/dd/yy), a two- letter code for a spe-
cific sampling location (e.g., IN for inlet water, PF for
before the filtration process, and AF for after the filtration
process or at the plant outlet), a one-letter code desig-
nating the analyses to be performed (see Table 3-1),
and a code indicating whether the sample is a primary
sample or a field duplicate sample. A field duplicate was
identified by adding a "dup" to the label and a primary
sample used no additional coding.
AC-02/15/98-PF-B-DUP
Date: 02/15/98 Time: 11a.m.
Collector's Name: Sample Collector
Location: Any City WTP
Sample ID: AC-02/15/98-PF-B-DUP
Send to: Battelle
Analysis Required: Total As, Al, Fe, and Mn
Preservative: 0.05% sulfuric acid
Figure 3-1. Example of Sample Bottle Label
After the sample bottles were labeled, they were placed
in coolers subdivided into three compartments, each cor-
responding to a specific sampling location at each plant.
Color coding was used to identify sampling locations and
all associated sample bottles. For example, red, blue,
and yellow were used to designate sample locations for
raw water at the plant inlet, before the filtration process,
and after the filtration process (or at the plant outlet),
respectively. Other sampling and shipping-related materi-
als, including latex gloves, chain-of-custody forms, pre-
paid Federal Express air bills, sampling instructions, ice
packs, and bubble wrap, also were packed into coolers.
When arsenic speciation or recycle supernatant/super-
natant discharge samples were to be collected, arsenic
speciation kits or recycle supernatant/supernatant dis-
charge sampling kits also were included in the cooler.
After preparation, sample coolers were sent to all plants
every Thursday via Federal Express for the following
week's sampling activity. Figure 3-2 shows photographs
of a sample cooler with three sample compartments and a
color-coded instruction sheet placed under the lid of the
cooler.
3.3 Sampling Procedures
3.3.1 General Approach and Sampling
Schedules
Two Battelle staff members traveled to each plant to col-
lect source water samples, meet plant operators, solicit
interest in participating in this year-long sampling pro-
gram, and obtain plant design and operating information
and historical water quality data. After the plant selection,
one Battelle staff member returned to each plant to collect
samples at selected sampling locations and train the plant
operator or a designated POC to perform sampling and
field arsenic speciation. The remaining three preliminary
sampling events and long-term sampling events then
were conducted by the trained plant personnel. Residuals
sampling, including a single sludge sampling event (Plant
A only) and the monthly collection of recycle supernatant
or supernatant discharge, also were collected by the
designated plant employees with detailed instructions
provided by Battelje over the telephone. Table 3-2 sum-
marizes the sampling activities at both plants.
During the preliminary and long-term sampling, sample
collection was conducted on a four-week cycle, with each
week having unique sampling requirements. Table 3-3
summarizes the schedules for the initial source water,
the preliminary, the long-term, and the sludge sampling
at both plants.
After receipt of the weekly sample coolers, plant personnel
began sampling activities at the selected locations on the
scheduled dates. Upon completion, all sample bottles were
placed in the same coolers for return shipment to Battelle
by Federal Express. Upon receipt of the samples, the des-
ignated Battelle sample custodian immediately examined
and compared the conditions of all sample bottles with
those indicated on the chain-of-custody forms. Samples
then were distributed to Battelle's ICP-MS laboratory and
Wilson Environmental Laboratories for chemical analyses.
Throughout the duration of the study, Battelle staff main-
tained frequent telephone contact with each plant to
ensure that all sampling activities were carried out as
planned. For example, after scheduled arrival of sample
coolers, one Battelle staff member would call to confirm
the receipt of the coolers, answer any questions, discuss
irregular plant operations and unusual observations, and
propose/suggest corrective actions. When available, re-
sults of the chemical analyses also were discussed over
the telephone and data sheets were sent quarterly to the
plants for review. Further, plant operational and water
quality data (such as plant flowrate, chlorine addition
rate, and turbidity) were sent along with sample coolers
or transmitted via facsimile to Battelle for information/
evaluation.
-------
Table 3-2. Summary of Sampling Activities at Plants A and B
Sampling Activities
Initial source water sampling
Preliminary sampling
Long-term sampling
Sludge sampling
Recycle water sampling
Sampling
Frequency
Once
Weekly
Weekly'"
Once
Weekly
Plant A
02/10/98
4/22/98 through 5/1 3/98
6/24/98 through 06/1 6/99
• 11/18/98
1 1/1 1/98 through 06/16/99
Plant B
02/4/98
5/7/98 through 5/28/98
6/1 1/98 through 12/8/98
NS
11/1 0/98 through 1/1 5/99
(a) Exceptforthe weeks of 11/23/98,12/21/98, and 12/28/98.
NS = Not sampled.
Table 3-3. Summary of Sampling Schedule for Plants A and B
Water Sampling
Analyte
As (total)
As (total soluble)
As (paniculate)
As (III)
As(V)
Al (total)
Fe (total)
Mn (total)
Al (dissolved)
Fe (dissolved)
Mn (dissolved)
Alkalinity
Sulfate
NOa-NO, (N)
TOG
Turbidity
pH
Hardness
Ca Hardness
Mg Hardness
TCLP Metals
Percent Moisture
PH
As (total)
Fe (total)
Mn (total)
Initial Source
Water Sampling
(Once)
W*
W*
W*
W*
W*
W*
W*
W*
W*
W*
W*
W*
W*
W*
W*
W*
W*
Preliminary Sampling Cycle
Weekl Week 2 Weeks Week 4
W* W W W
W*
W*
W*
W*
W*
W* W W W
W* W W W
W* W W W
W*
W* W W W
W*
W*
W*
Week
W*
W*
W*
W*
W*
W*
W*
W*
W*
W*
W*
W
W
W
W
W
W
Long-Term Sampling Cycle
1 Week 2 Weeks Week 4
W W, R* W
R*
R*
W W, R* W
W W, R* W
W W, R* W
R*
R*
R*
W* W, W
W* W, R* W
Sludge
Sampling
(Once)
S
S
S
S
S
S
Duplicate samples collected and analyzed.
Wa Water samples collected from the inlet, prefiltration, and after-filtration locations (Plants A and B) and from after-softening location (Plant A
only).
A a Recycle supernatant sample collected at Plant B; supernatant discharge sample collected at Plant A.
S » Sludge samples collected at Plant A.
Empty cells indicate no samples taken.
3.3.2 Arsenic Field Speciation Procedure
The procedures for performing field arsenic speciation are
shown in Figure 3-3 and are described as follows ("steps"
refer to Figure 3-3):
• Bottle A: A 400-mL disposable plastic beaker was
rinsed thoroughly with the water to be sampled.
The beaker then was used to collect a water sam-
ple and to fill bottle A with an aliquot of that sample
(step 3). If necessary, additional sample water was
added to the beaker after bottle A was filled to
complete arsenic speciation sampling.
Bottle B: A 60-mL disposable plastic syringe was
rinsed thoroughly with the water in the plastic
beaker by completely filling and emptying the
syringe (step 4). After attaching a 0.45-um disc
filter and wasting about 10 drops of the filtrate, the
syringe was used to filter the water sample from
10
-------
Figure 3-2. Photographs of a Typical Sample Cooler (with Three Sample Compartments) and a Color-
Coded Instruction Sheet
the beaker and fill bottle B. Bottle B then was
tightly capped and vigorously shaken for about
15 seconds to allow thorough mixing of the filtered
water and sulfuric acid (step 5).
Bottle C: The protective caps on the top and
bottom of a resin column were removed and
approximately 40 mL of the water in bottle B was
wasted through the column. This initial 40 mL was
used to displace the water in the resin column and
to ensure attainability of a representative sample
from the column. The resin column then was posi-
tioned over bottle C, and the water from bottle B
was passed through the column until approxi-
mately 20 mL of the resin-treated sample had
been collected in bottle C (step 6).
The procedure as described under the above three bul-
lets was repeated to obtain duplicate bottles A, B, and C.
11
-------
Step 1:
Go to sampling point
(Inlet, Pre-Filtration, or Outlet)
Step 2:
Put on gloves
Stop 3:
Collect water sample
Preservative
a) Avoid agitation
b) Fill bottle A
Important Note;
DO NOT RINSE ANY BOTTLES!!
THEY CONTAIN PRESERVATIVES!!
Step 4:
Prepare the syringe
Fill and empty syringe to rinse
Step 5:
Collect filtered sample
V
Preservative
(H2S04)
B
a) Refill syringe
b) Attach filter to syringe c) Fill bottle B
and waste 10 drops
d) Cap tightly; shake (about 15 seconds)
Step 6:
Collect resin-treated sample
A
a) Fill resin column from bottle B;
drain column to rinse; repeat
(waste approx. 40 mL)
Preservative
(HNOg)
b) Drain column into bottle C;
repeat (collect approx. 20 mL)
Step 7;
Fill in all blanks on chain-of-custody form
mi
Step 8;
Pack and ship samples
a) Tighten caps of all bottles b) Tape cooler before shipping
Figure 3-3. Instruction Sheet for Arsenic Field Speciation
12
-------
Upon completion, the individual performing the specia-
tion signed on a chain-of-custody form (step 7). All sam-
ple bottles (for arsenic speciation and other water quality
parameters), along with the signed chain-of-custody form,
were placed in the original cooler with ice packs and
shipped via Federal Express to Battelle (step 8).
3.3.3 Recycle Supernatant/Supernatant
Discharge Sampling Procedure
Figure 3-4 shows an instruction sheet for performing re-
cycle supernatant and supernatant discharge sampling.
Because both total and dissolved As, Al, Fe, and Mn
were analyzed, the procedure for recycle supernatant/
supernatant discharge sampling was similar to that for
arsenic speciation, except that the steps for collecting
samples in bottle C were omitted.
3.3.4 Sampling Procedure for Other Water
Quality Parameters
All other water quality parameters identified in Table 3-3,
were analyzed using samples either in bottles A, B, and
C or in bottles provided by Wilson Environmental Labor-
atories (i.e., bottles D, E, F, and G). All bottles D, E, F,
and G were filled directly from sample taps and pre-
served according to the respective analytical methods.
These sample bottles along with bottles A, B, and C
were placed in the original coolers with ice packs and
shipped via Federal Express to Battelle.
3.4 Analytical Procedures
The analytical procedures used for this project were de-
scribed in Section 4.0 of the QAPP prepared by Battelle
(1998). Table 3-4 presents a summary of all analytical
methods used. All of the methods used are standard
EPA methods. Analyses of As, Al, Fe, and Mn in water
samples were accomplished by ICP-MS using EPA
Method 200.8. ICP-MS was chosen as the method for
As, Al, Fe, and Mn analyses because it had a low meth-
od detection limit (MDL) and was a relatively low-cost
method (about $35/sample). ICP-MS analyses were con-
ducted on a Perkin Elmer Sciex Model 6000 equipped
with a crossflow pneumatic nebulizer and an automatic
sampler. Yttrium (""Y) was added to all samples as an
internal standard to correct for instrument drift. Because
arsenic is monoisotopic, all measurements were made at
a mass/charge ratio of 75. To eliminate an appreciable
interference from a chloride molecular species ("Ar^CI),
all ion current data at m/e 75 were corrected using chlo-
ride measurements in all samples, and the MDL was
0.1 ug/L As. All the unfiltered water samples (i.e., in bot-
tle A) were digested using EPA Method 200.8 prior to
analysis. Filtered water samples (i.e., in bottles B and C)
were analyzed directly without digestion. Wilson Environ-
mental Laboratories in Westerville, OH was subcontracted
to perform all other chemical analyses. QA/QC of all
methods followed the guidelines provided in the QAPP
(Battelle, 1998), and the data quality in terms of precision,
accuracy, MDL, and completeness is discussed in Sec-
tion 5.0 of this report.
It should be noted that turbidity tests were not run on site.
Relatively high levels of reduced iron in raw water sam-
ples may have oxidized during transportation of samples
to the analytical laboratory, resulting in elevated turbidity
readings. The turbidity might have been much lower if
readings had been taken on site.
13
-------
Step 1:
Go to reclaimed backwash water
or supernatant discharge
sampling point
Step 2;
Put on gloves
Important Note;
DO NOT RINSE ANY BOTTLES!!
THEY CONTAIN PRESERVATIVES!!
Step 3;
Collect water sample
Preservative
(HN03)
a) Avoid agitation
b) Fill bottle A
Step 4:
Prepare the syringe
Fill and empty syringe to rinse
Step 5;
Collect filtered sample
V
a) Refill syringe
b) Attach filter to syringe
and waste 10 drops
-Preservative
I/ (HN03)
c) Fill bottle B
Step 6;
Fill in all blanks on chain-of-custody form
ffl
Step 7:
Pack and ship samples
a) Tighten caps of
all bottles
EPA15.CDR
b) Tape cooler before shipping
Figure 3-4. Instruction Sheet for Recycle Supernatant/Supernatant Discharge Sampling
14
-------
Table 3-4. Summary of Analytical Methods for Arsenic Treatment Study
Sample Matrix
Aqueous (including samples collected at the
plant inlet, before the filtration process, after the
filtration process, and supernatant water from
sludge settling ponds/lagoons that was recycled
or discharged)
Sludge
Analyte
As (total)
Total Al
Total Fe
Total Mn
Alkalinity
PH
Turbidity
Hardness
so,2-
TOC
NO37NO2-
Water content
PH
TCLP metals
Total As
Total Fe
Method
EPA 200.8
EPA 200.8
EPA 200.8
EPA 200.8
EPA 31 0.1
EPA 150.1
EPA 180.1
EPA 215.1/242.1
EPA 375.4
EPA 41 5.1
EPA 353.2
ASTMD2216
SW-846 9045
SW-8461311
SW-846 3051 ,6020
SW-846 3051, 6020
Analytical Laboratory
Battelle ICP-MS
Battelle ICP-MS
Battelle ICP-MS
Battelle ICP-MS
Wilson Environmental
Wilson Environmental
Wilson Environmental
Wilson Environmental
Wilson Environmental
Wilson Environmental
Wilson Environmental
Wilson Environmental
Wilson Environmental
Wilson Environmental
Wilson Environmental
Wilson Environmental
ASTM = American Society for Testing and Materials.
15
-------
4.0 Results and Discussion
This section presents the results of the treatment plant
selection process, which resulted in the selection of two
iron removal plants, referred to as Plants A and B. In
addition, results from water and residuals sampling and
analysis at each plant are summarized and discussed.
Complete analytical results from long-term water sam-
pling at Plants A and B are presented in Appendices A
and B, respectively.
4.1 Plant Selection
The plant selection process consisted of identifying po-
tential treatment facilities, contacting these facilities via
telephone, and conducting initial site visits during which
source water samples were collected and analyzed. Ini-
tially, a list was prepared consisting of eight potential iron
removal treatment facilities. These candidate facilities
were contacted to discuss the study and determine de-
tails of plant operation. Each facility was evaluated and
assigned an overall plant rating based on the following cri-
teria: source water arsenic concentrations, source water
type, availability of manpower to conduct study, avail-
ability of historical data, and plant size. Selection was
based primarily on source water arsenic concentrations,
and preference was given to facilities with arsenic con-
centrations greater than 20 ug/L Another major con-
sideration was the availability of manpower, because the
long-term study would require significant resources. Also,
it was desirable to have historical arsenic analytical data,
fairly large facilities (i.e., >20,000 people served), and a
mix of plants using ground water and/or surface water
sources.
From the eight initial plants, two iron removal plants
were selected for site visits and source water sampling
(see Table 4-1). The same plants that were selected for
the initial site visits also were selected for the sub-
sequent phases of the study. Results from sampling at
both facilities during each phase of the study are pre-
sented in the sections that follow.
4.2 Plant A
Water and residual samples were collected and analyzed
at Plant A during three phases of the study. The first
phase consisted of source -water sampling, which was
used to help determine if the plant should be considered
for further evaluation. Source water sampling at Plant A
was performed in February 1998. Following source water
sampling, the second phase of the study was initiated.
This second phase consisted of weekly water sampling
for a four-week period in April and May 1998 and was
designed to determine if the sampling locations and pro-
posed water quality analyses were appropriate for the
third phase, long-term evaluation. The third phase was
initiated in June 1998 and continued through June 1999.
This long-term evaluation consisted of weekly sampling
and analysis of process water at four locations through-
out the treatment process. Also, arsenic speciation sam-
pling was conducted every fourth week. The third phase
of the study also included residual sample collection and
analysis. Supernatant discharge samples from the set-
tling pond were collected monthly beginning in November
1998, and three sludge samples were collected during a
single sampling event from the settling pond.
Table 4-1. Initial List of Treatment Facilities Identified for the Study
Source Water Arsenic
Source Water Arsenic
Plant
ID
A
B
Concentration, March 19951"1
Process (M9/L)
Iron removal
Iron removal
30.2
Not sampled
Concentration, September 1997"" Population
(ug/L) Served
Not sampled
65
15,000
Up to 20,000
Historical
Data
Yes
Yes
Source Water
Type
Ground water
Surface water
(a) Results provided by treatment facility.
16
-------
4.2.1 Plant A Description
4.2.2 Initial Source Water Sampling
Plant A is one of three plants that provides water to a
city with a population of approximately 15,000 (approxi-
mately 6,000 connections). Plant A was built in 1970 and
treats ground water using an iron removal process fol-
lowed by zeolite softening. The plant is capable of treat-
ing 1.6 million gallons per day (mgd). A schematic diagram
of the Plant A treatment process is shown in Figure 4-1.
The treatment process consists of the following major
elements:
• Aeration. Aeration is used to oxidize iron and
manganese as well as remove H2S, NH3, SO2, and
CH,
• Chlorination. Approximately 5 mg/L total chlorine
(1.5-2 mg/L free chlorine) is added to oxidize
remaining iron and manganese and to disinfect
filters and softeners.
• Sedimentation. Sedimentation occurs in a baffled
basin with approximately 20 minutes retention
time. After sedimentation, potassium perman-
ganate (KMnO4) is added to remove manganese,
taste, and odor as well as to continuously regen-
erate the manganese greensand in the filter.
• Filtration. The filtering media consists of
manganese greensand (top) and graded gravel
(bottom). A water backwash occurs every 20 hours
and an air backwash occurs every 72 hours.
• Softening. Approximately two thirds of the filtered
water is sent through a zeolite resin softener (ion
exchange) to reduce hardness. Regeneration
occurs every 175,000 gal processed with 27%
solution of NaCI. The regeneration takes approxi-
mately 1 hour and consists of a 12-minute back-
wash, 20-minute brine rinse, and a slow/fast rinse
cycle.
• Postchlorination. Approximately 5 to 6 mg/L of
total chlorine (<1 mg/L free chlorine) is added for
distribution residual. Also, 0.9 to 1.2 mg/L of
fluoride (H2SiF6) is added. No ammonia is added
because the water contains NH3 and about 0.8 to
1.0 mg/L of residual chloramines is maintained in
the finished water.
• Backwash. Backwash water and regenerant
waste is sent to an outdoor settling pond and
supernatant is discharged to the sanitary sewer.
Sludge is sent to wastewater plant drying beds and
then to local farm fields. No arsenic sampling on
sludge had been conducted prior to this study.
Plant A obtains source water from three ground water
wells (Wells 5, 6, and 7). Each well is approximately
275 ft deep. An initial site visit to Plant A was conducted
February 10, 1998 during which time source water sam-
ples were collected from the intake, which represents a
combined sample from ground water Wells 5, 6, and 7.
The total arsenic concentration during the initial sam-
pling event was 23.5 ug/L. Particulate arsenic accounted
for 1.7 ug/L of the total arsenic concentration, and solu-
ble arsenic accounted for the remaining 21.8 ug/L. Field
arsenic speciation sampling indicated that the soluble
arsenic consisted of 20.1 ug/L of As(lll) and 1.7 ug/L of
As(V), which was consistent with what would be ex-
pected for a ground water source. Also, as would be
expected at an iron remova] plant, the total iron concen-
tration was relatively high, 2,700 ug/L. Table 4-2 presents
the complete analytical results from the initial source
water sampling event.
Due primarily to the relatively high source water arsenic
concentrations and the availability of plant personnel to
perform preliminary and long-term sampling, Plant A was
selected for incorporation into the preliminary and long-
term evaluation phases of this project.
4.2.3 Preliminary Sampling
During the preliminary sampling phase of this study,
water samples were collected at four locations within the
treatment plant: inlet (IN), before filtration (PF), after fil-
tration (AF), and after softening (AS). The IN samples
were collected from a tap located prior to treatment and
represents combined water from Wells 5, 6, and 7. The
PF samples were collected after the water had under-
gone aeration, chlorination, and sedimentation.
After filtration and prior to zeolite softening, the AF sam-
ples were collected. Finally, the AS samples were col-
lected after softening and prior to final chlorination and
H2SiF6 addition. Figure 4-2 is a process flowchart for
Plant A that shows sampling locations within the treat-
ment process and the associated sample analyses per-
formed at each location.
Alkalinity, pH, total iron, total manganese, and total ar-
senic analyses were performed on samples collected at
each of the four sampling locations each week. Turbidity,
hardness, and arsenic speciation analyses were con-
ducted once during the preliminary study on samples
collected at each sampling location. Soluble and particu-
late arsenic were determined as part of the arsenic
17
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Table 4-2. Source Water Analytical Results at Plant A (February 10, 1998)
Parameter
Alkalinity
Sulfate
Turbidity
PH
Hardness
Ca Hardness
Mg Hardness
Total AI
Total Fe
Total Mn
NO3-NO2 (N)|b)
TOO
As (total)
As (total soluble)
As (particulate)
As (III)
As(V)
Unit
mg/L">
mg/L
NTU
mg/Lw
mg/L("
mg/Lw
M9/L
Mg/L
Mg/L
mg/L
mg/L
M9/L
M9/L
M9/L
M9/L
ug/L
Primary
Sample
413
<1
25
7.6
270
140
130
400
2,640
<20
<0.02
6
23.5
21.9
1.6
19.7
2.2
Duplicate
Sample
412
<1
24
7.6
270
137
133
400
2,760
<20
<0.02
7
23.4
21.6
1.8
20.5
1.1
Average
412.5
<1
24.5
7.6
270
138.5
131.5
400
2,700
<20
<0.02
6.5
23.5
21.8
1.7
20.1
1.7
(a) AsCaCO3.
(b) Combined NO3-N and NO.
ND = not detected.
TOC = total organic carbon.
,-N.
speciation, as well as the species (arsenite and arse-
nate) making up the soluble fraction of the total arsenic
concentration. Table 4-3 presents the results from the
four-week preliminary sampling period.
Results from the preliminary sampling events indicated
that inlet total arsenic concentrations ranged from ap-
proximately 23.7 to 18.6 ug/L. Consistent with the initial
source water sampling, the source water contained
primarily As(lll) and minor concentrations of As(V) and
particulate arsenic. As would be expected following chlo-
rination and sedimentation, As(lll) had been almost com-
pletely oxidized to As(V) at the PF sampling location. It
appeared that, after the As(lll) had been oxidized to
As(V), it coprecipitated with the oxidized iron. Therefore,
at the PF sampling location, arsenic was present pri-
marily as particulate. The majority of the arsenic removal
occurred during filtration. No significant removal occurred
during sedimentation or softening.
The average total arsenic removal by Plant A was approx-
imately 91% during the preliminary sampling, reducing the
finished water total arsenic concentration to between 3.4
and 0.6 ug/L. McNeill and Edwards (1997) developed the
following simplified model for predicting arsenic removal
during metal hydroxide precipitation based on raw water
Fe and AI concentrations:
Arsenic Sorbed(%) = 100 x -
where K = 78 mM~
Kx[Fe + Al]mM
+ Kx[Fe + Al]mM)
(D
This model was based on data collected at more than 14
full-scale facilities, and was able to accurately predict
arsenic removal within ±13% (90th percentile confidence
interval). Applying this model to the preliminary results
from Plant A, the predicted removal ranged from 77% to
79% compared to actual removal rate ranging from 84%
to 97%. The maximum difference between the actual
and predicted arsenic removal efficiencies was 10%. It
should be noted that the calculation did not incorporate
aluminum concentrations because they were not ob-
tained during the preliminary sampling phase. Neverthe-
less, the simplified model appeared to approximate the
arsenic removal at Plant A fairly well, and was used to
evaluate long-term system performance.
Other water quality parameters were analyzed to support
understanding of mechanisms of arsenic removal. Dur-
ing preliminary sampling, pH was relatively constant, at
approximately 7.7 throughout the treatment process. This
pH is in the range where no effect on arsenic removal
efficiency using iron hydroxide precipitation has been ob-
served in previous studies (Sorg and Logsdon, 1978;
Sorg, 1993; Hering et al., 1996).
Oxidation of Fe(ll) by chlorine may be described by the
following chemical reaction:
CI
6H2O
2Fe(OH)3(s) + 2CP + 6H* (2)
The slight decrease in alkalinity observed after oxidation of
the iron (i.e., at the PF sampling location) is a result of stoi-
chiometry of iron oxidation in which protons are produced
and alkalinity is destroyed (Benefield and Morgan, 1990).
19
-------
MONTHLY
As (total), As (III), As (V), Turbidity,
Hardness, Dissolved Al, Fe, and Mn
SLUDGE SENT TO DRYING BEDS,
THEN TO LOCAL FARM FIELDS
As (total), Percent moisture, pH,
TCLP metals, Total Al, Fe, and Mn
INFLUENT
SETTLING
POND
WEEKLY
As (total), Alkalinity, pH,
Total Al, Fe, and Mn
AERATION
SUPERNATANT WATER
AND WASTEWATER
DISCHARGED TO "
SANITARY SEWER
Sludge
(Yearly Basis)
SEDIMENTATION
Plant A
Iron Removal
Design Flow: 1.6 mgd
©-
r \ w As (dissolved and total), pH,
1 *" Al, Fe, and Mn (dissolved and total)
As (total), As (III), As (V),
Turbidity, Hardness,
Total Al, Fe, and Mn
Backwash Water
As (total), Alkalinity, pH,
Total Al, Fe, and Mn
FILTRATION
(GREENSAND)
As (total), As (III), As (V),
Turbidity, Hardness,
Tota! Al, Fe, and Mn
Regenerant Waste
As (total), As (III), As (V),
Turbidity, Hardness,
Total Al, Fe, Mn
ZEOLITE
SOFTENING
Approx 2/3 of Flow Treated
Using Zeolite Softening
As (total), Alkalinity, pH,
Total Al, Fe, and Mn
As (total), Alkalinity, pH,
Total Al, Fe, and Mn
1 '
DISTRIBUTION
SYSTEM
LEGEND
O Water Sampling
Location
x"~x Sludge Sampling
( SS ) Location
Disinfectant Addition
Dninf
Unit Process
„,. _ Chemical Added to
KMnO, TT ..„
4 Unit Process
Figure 4-2. Process Flow Diagram and Sampling Locations at Plant A
20
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The source water at Plant A would be classified as hard
to very hard and the zeolite softening process effectively
reduced hardness from approximately 304 mg/L (as
CaCOa) to 11 mg/L (as CaCO3). As stated previously,
approximately two-thirds of the water processed at Plant
A is treated using zeolite softening. Turbidity also was
effectively removed at Plant A with concentrations de-
creasing from approximately 23 NTU to 5.2 NTU follow-
ing aeration, chlorination, and sedimentation. Relatively
high turbidity concentrations at the inlet may be a result
of iron oxidation after the sample was collected and prior
to analysis. After filtration the turbidity decreased to ap-
proximately 0.3 NTU. Total manganese concentrations
were relatively constant throughout the treatment process
with concentrations ranging between 60 and <20 ug/L.
Total iron concentrations ranged from 2,390 to 2,635 ug/L
in the source water and <30 to 50 ug/L in the finished
water. Total iron concentrations were relatively constant
between the plant inlet and prior to filtration, with signifi-
cant iron removal occurring as a result of filtration. It
appears that the primary arsenic removal mechanism at
Plant A is adsorption and coprecipitation of As(V) with
the iron hydroxide precipitates.
Based on the results of the preliminary sampling effort,
only minor changes were made to the approach for the
long-term evaluation. Sampling locations and primary
analytes remained unchanged, except for the addition of
aluminum. The iron and manganese analysis was modi-
fied to achieve lower detection limits by using ICP-MS.
Also, it was determined that part of the sample in bot-
tle B from the arsenic speciation kits would be used to
determined dissolved aluminum, iron, and manganese
concentrations.
4.2.4 Long-Term Sampling
Long-term sampling and analysis consisted of 49 weeks
of sampling with 12 arsenic speciation sampling events.
During the long-term sampling phase of this study, water
samples were collected at the same four locations that
were used during the preliminary sampling phase. Alka-
linity, pH, total arsenic, total aluminum, total iron, and
total manganese analyses were performed on sampled
collected each week. Arsenic speciation sampling was
conducted 12 times during the long-term sampling phase
on samples collected from each sampling location. Dis-
solved aluminum, iron, and manganese concentrations
at each sampling location were determined monthly
using a sample from bottle B of the arsenic speciation
kits. Additionally, residual sampling was performed dur-
ing this phase and consisted of collection and analysis of
supernatant discharge and sludge from the settling pond.
The following subsections summarize the analytical results
for arsenic, other water quality parameters, and residuals.
Figure 4-2 is a process flow diagram for Plant A that
indicates sampling locations during the long-term eval-
uation and the analyses performed on samples at each
location.
4.2.4.1 Arsenic
Table 4-4 provides a summary of the arsenic analytical
results collected at the four treatment process locations.
Total arsenic concentrations at the inlet ranged from
12.5 ug/L to 42.5 ug/L, with an average concentration of
20.7 ug/L. These concentrations were basically consist-
ent with what had been observed during the preliminary
phases of the study. Total arsenic concentrations at the
Table 4-4. Summary of Arsenic Analytical Results at Plant A (June 24,1998-June 16,1999)
Parameter
As (total)
As (total soluble)
As (particulate)
As (III)
As(V)
Sample Location
Inlet
Prefiltration
After filtration
After softening
Inlet
Prefiltration
After filtration
After softening
Inlet
Prefiltration
After filtration
After softening
Inlet
Prefiltration
After filtration
After softening
Inlet
Prefiltration
After filtration
After softening
Units
Pg/L
Pg/L
|jg/L
Pg/L
M9/L '
Pg/L
Pg/L
Pg/L
Pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
Number of
Samples
49
49
49
49
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
Minimum
Concentration
12.5
3.8
1.0
0.8
15.1
3.1
2.3
1.7
<0.1
10
<0.1
<0.1
10.8
0.1
0.1
<0.1
1.1
2.7
2.0
1.2
Maximum
Concentration
42.5
23.8 •
8.0
10.1
25.4
10
4.1
10.2
4.9
17.9
5.1
<0.1
21.3
4.8
0.8
0.8
10.8
5.4
3.6
10.2
Average
Concentration
20.7
19.3
3.1
2.8
20.3
5.3
3.0
4.0
1.8
14.3
0.8
<0.1
16.0
0.9
0.4
0.5
4.3
4.0
2.5
3.1
Standard
Deviation
3.8
4.0
1.1
0.1
3.7
2.3
0.5
2.5
2.1
2.4
1.5
NA
3.7
1.3
0.2
0.3
2.4
0.8
0.5
2.6
22
-------
PF sampling location ranged from 3.8 jig/L to 23.8 ja.g/L,
with an average of 19.3 ng/L It should be noted that only
three sampling events produced approximately 3 to 6 |ig/L
of arsenic at the PF location. Therefore, only minor arse-
nic removal occurred during the sedimentation process.
Samples collected after filtration contained total arsenic
concentrations ranging from 1.0 jig/L to 8.0 jig/L, with an
average of 3.1 jxg/L; and total arsenic concentrations aver-
aged 2.8 (ig/L in samples collected after the zeolite soft-
ening process. The data indicate that the majority of the
arsenic removal occurred in the filters.
The average removal percentage of total arsenic between
the IN and AF sampling locations was 85% and between
the IN and AS locations was 87%. These data indicate
that the vast majority of the arsenic was removed during
filtration and that the softening process did little to improve
removal efficiency. The average arsenic removal pre-
dicted by McNeill and Edwards (1997) sorption model was
76%, which is within the 90th percentile confidence inter-
val of the model. Figure 4-3 is a graph showing the total
arsenic concentration recorded at each sampling location
throughout the study, as well as the removal percentage
calculated for each sampling event. As shown in this fig-
ure, total arsenic concentrations at the IN and AF sam-
pling locations remain relatively constant throughout the
study with no seasonal effects noted. The three dips in
the arsenic concentrations at the PF sampling location
may have been a result of reduced process flow occurring
during the winter months, resulting in longer retention
times in the sedimentation basins.
Particulate arsenic concentrations averaged 1.8 jig/L at
the inlet, 14.3 ng/L before filtration, 0.8 jag/L after filtra-
tion, and <0.1 after softening. The increase in particulate
arsenic at the PF sampling location was due to sorption
and coprecipitation of arsenic on/with iron hydroxide pre-
cipitates. This observation was supported by the de-
crease of particulate arsenic in the AF sampling location.
As(lll) and As(V) make up the soluble portion of the total
arsenic concentration. The average As(lll) and As(V) con-
centrations in the source water were 16.0 and 4.3 ng/L,
respectively. The As(lll) was oxidized to As(V) by chlo-
rination prior to the PF sampling location and the As(V)
was sorbed to and coprecipitated with the iron hydroxide.
Therefore, the majority of the total arsenic in the water
prior to filtration was in particulate form (i.e., attached to
the iron). Average As(lll) concentrations remained low
and relatively constant following oxidation and the aver-
age As(V) concentrations decreased slightly from 4.3 jj,g/L
in the source water to 3.1 ng/L after softening.
100%
-Inlet
- Prefiltration
-After Filtration
-After Softening
-% Removal
6/4/98 7/24/98 9/12/98 " 11/1/98 12/21/98 2/9/99 3/31/99 5/20/99 7/9/99
Date
Figure 4-3. Total Arsenic Analytical Results During Long-Term Sampling at Plant A
23
-------
Figure 4-4 shows As(lll), As(V), and particulate arsenic
concentrations measured during the long-term evalu-
ation.
Plant A water treatment system was able to consistently
remove arsenic to low levels (i.e., average treated water
total arsenic concentration was 2.8 ug/L). The primary
arsenic removal mechanism appears to be coprecipi-
tation with iron hydroxide precipitates followed by filtra-
tion. The simplified sorption model developed by McNeil!
and Edwards (1997) appears to approximate the arsenic
removal process at Plant A reasonably well, although the
model consistently underestimated the removal by ap-
proximately 11%.
4.2.4.2 Other Water Quality Parameters
In addition to arsenic analysis, other water quality param-
eters were analyzed to provide insight into the chemical
processes occurring at the treatment facility. Table 4-5
summarizes the analytical results for several water qual-
ity parameters obtained during the long-term sampling at
Plant A.
Alkalinity concentrations were relatively constant ranging
between 347 mg/L and 415 mg/L (as CaCO3) in the
source water, with an average of 413 mg/L. As observed
during the preliminary sampling, a slight decrease in
average alkalinity to 398 mg/L was observed after oxi-
dation of the iron due to the stoichiometry of iron oxida-
tion process. Turbidity concentrations ranged from 13.8
NTU to 26 NTU, with an average of 19 NTU. Increased
turbidity concentrations may have resulted from oxidation
of iron occurring after the sample was collected and prior
to analysis at the laboratory. The bulk of the turbidity was
removed during sedimentation, reducing concentrations
to an average of 5.1 NTU. The system effectively re-
moved turbidity with an average finished water concen-
tration of 0.1 NTU. Figure 4-5 plots inlet alkalinity, pH,
and hardness concentrations observed throughout the
duration of the study.
The pH was constant, averaging 7.6 or 7.7 at each sam-
pling location within the treatment process. This pH is in
the range (pH 5.5 to 8.5) where arsenic removal
efficiency by iron oxides is not affected (Sorg and
Longsdon, 1978; Sorg, 1993; Hering et al., 1996). Total
hardness concentrations ranged from 286 mg/L to
432 mg/L (as CaCO3) in the plant source water, with an
average of 316 mg/L. These concentrations were rela-
tively constant with the exception of the sample collected
on September 30, 1998. Similar to alkalinity, a slight
decrease in hardness was observed following oxidation of
iron, resulting in an average hardness concentration of
291 mg/L. As would be expected, considerable removal
of hardness was observed following zeolite softening,
reducing total hardness to an average of 5.2 mg/L (as
CaCO3).
Total iron concentrations at the inlet sampling location
ranged from 762 ug/L to 3,289 |jg/L and averaged 2,284
ug/L. At the PF sampling location, total iron concentra-
tions ranged from 267 ug/L to 3,026 ug/L and averaged
2,241 ug/L. Therefore, the total iron concentrations were
relatively constant between the source and just prior to
the filters. However, dissolved iron analytical results
show that approximately half of the iron entering the
plant was in the reduced form. The average dissolved
iron concentration in source water was 953 ug/L. After
aeration and chlorination, practically all iron was oxidized
with concentrations of <30 ug/L at all other sampling
locations throughout the study. The filtration process
removed most of the iron, reducing average total iron
concentrations to 71.5 ug/L. The zeolite softener filtered
additional iron particles and the average total iron con-
centration after the softening process was <30 ug/L. As
stated previously, iron is the key factor in arsenic
removal at Plant A. It is believed that the majority of the
arsenic removal is through adsorption and coprecipita-
tion of As(V) with iron hydroxides.
Total aluminum concentrations averaged 17.9 ug/L at
the inlet and <11 ug/L at the other three sampling loca-
tions. Concentrations of dissolved aluminum averaged
20.4 ug/L in the source water and <11 ug/L at the other
three sampling locations. It did not appear that co-
precipitation with aluminum hydroxide was a significant
factor in the removal of arsenic, because only minor con-
centrations were present.
Total and dissolved manganese concentrations were rel-
atively low. Total manganese concentrations averaged
22.2 ug/L in the source water, 42.4 ug/L prior to filtration,
22.7 ug/L after filtration, and 5.1 ug/L after softening.
The increase in manganese prior to filtration is most
likely due to the addition of KMnO4 for the greensand fil-
ters. Average dissolved manganese concentrations were
21.0 ug/L in the source water, 17.5 ug/L prior to filtration,
9.0 ug/L after filtration, and 2.5 ug/L after softening.
4.2.4.3 Supernatant Discharge
Backwash water is generated from backwashing the
filtration units every 24 hours and from backwashing the
zeolite resin softeners after every 275,000 gallons pro-
cessed. All backwash water and regenerant waste at
Plant A is sent to an outdoor settling pond and super-
natant from the pond is discharged continuously to the
sanitary sewer. Supernatant discharge samples were
collected at the outfall of the settling pond into the sani-
tary sewer. Results of the supernatant discharge sam-
pling are summarized in Table 4-6.
24
-------
Inlet
30
25
20 •
e .
u
15 •
10 •
5 •
K<3^ j^ .fl)^ oS^ nSj^
^ oP>
d?> o?> ex* cP <^>
v*?1
30
Prefiltration
S
I
25
20
15
10 -
5
0
«•
S/////S//SSS
fiO rfO r«» fc>J i. V r^* rv V rvO rv^ rCQ i~!O
After Softening
-------
Table 4-5. Summary of Water Quality Parameter Analytical Results at Plant A (June 24,1998-June 16,1999)
Parameter
Alkalinity
Turbidity"1
pH
Total Hardness
Total Al
Total Fe
Total Mn
Dissolved Al
Dissolved Fe
Dissolved Mn
Sample
Location
Inlet
Prefiltration
After filtration
After softening
Inlet
Prefiltration
After filtration
After softening
Inlet
Prefiltration
After filtration
After softening
Inlet
Prefiltration
After filtration
After softening
Inlet
Prefiitration
After filtration
After softening
Inlet
Prefiltration
After filtration
After softening
Inlet
Prefiltration
After filtration
After softening
Inlet
Prefiltration
After filtration
After softening
Inlet
Prefiltration
After filtration
After softening
Inlet
Prefiltration
After filtration
After softening
Units
mg/L
mg/L
mg/L
mg/L
NTU
NTU
NTU
NTU
-
—
_
-
mg/L
mg/L
mg/L
mg/L
pg/L
pg/L
pg/L
Pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
Number of
Samples
49
49
49
49
12
12
12
12
49
49
49
49
11
12
12
12
49
49
49
49
49
49
49
49
49
49
49
49
12
12
12
12
12
12
12
12
12
12
12
12
Minimum
347
380
378
377
13.8
3.0
0.1
0.05
7.5
7.6
7.5
7.5
286
270
165
3.0
<11
<11
<11
<11
762
267
<30
<30
14.5
14.9
4.8
1.2
<11
<11
<11
<11
<30
<30
<30
<30
17.4
13.9
2.9
1.2
Maximum
415
415
409
414
26
7.2
2.3
0.3
7.8
8.0
8.0
8.1
432
308
317
11.4
324
35.9
22.8
34.4
3,289
3,026
440
128
57.3
694
95.8
24.3
121
24.1
51.8
68.6
1,943
<30
<30
<30
24.1
21.6
17.6
5.0
Average
413
398
393
394
19
5.1
0.5
0.1
7.6
7.7
7.6
7.7
316
291
280
5.2
17.9
<11
<11
<11
2,284
2,241
71.5
<30
22.2
42.4
22.7
5.1
20.4
<11
<11
<11
953
<30
<30
<30
21.0
17.5
9.0
2.5
Standard
Deviation
12.9
6.2
6.6
6.7
3.4
0.9
0.6
0.08
0.05
0.09
0.09
0.14
41.3
11.9
38.9
2.5
45.4
6.5
5.4
6.6
424
565
96.4
22.3
7.1
103
16.2
5.6
33.3
7.5
13.6
18.2
720
NA
NA
NA
2.2
2.3
4.1
1.4
(a) Inlet turbidity concentrations may be elevated due to oxidation of iron occurring after sample collection and prior to laboratory analysis.
The total arsenic concentrations in the supernatant dis-
charge ranged from 9.4 ug/L to 167.0 ug/L, with an aver-
age of 72.4 ug/L. Approximately 40% of the total arsenic
concentration was soluble and 60% was particulate. As
expected, the average iron concentration in the super-
natant water was relatively high at 5,780 ug/L. Practically
all of the iron is in the oxidized form. The particulate
arsenic is most likely sorbed to unsettled iron solids.
4.2.4.4 Sludge
Sludge is generated from cleaning sedimentation basins
and from backwashing the greensand filters and zeolite
resin softeners. The sedimentation basins are cleaned
out once per year, and the wastewater and sludge are
sent directly to the sanitary sewer. A water backwash is
performed on the greensand filters every 24 hours and
an air backwash is performed every 72 hours. Regener-
ation of the zeolite softeners occurs after every 275,000
gallons processed, and involves using a 27% solution of
NaCI. The regeneration takes about 1 hour to complete,
and consists of a 12-minute backwash, a 20-minute brine
rinse, and slow/fast rinse cycle.
The backwash water and regenerant waste are sent to
an outdoor settling pond. Historically, the retention pond
26
-------
45
40 .
35 -
30 -
25 .
20 -
15 -
10 -
500
-.450
--400
- . 350
. .300
-.250
. . 200
150
.. 100
50
-pH (units)
- Hardness (mg/L as CaCOj)
-Alkalinity (mg/L as CaCQj)
6/4/98 7/24/98 9/12/98 11/1/98 12/21/98 2/9/99 3/31/99 5/20/99 7/9/99
Date
Figure 4-5. Inlet pH, Hardness, and Alkalinity Analytical Results at Plant A
was drained and the sludge removed once per year.
Sludge then was transferred to the municipal wastewater
treatment plant and placed on the wastewater plant
drying beds. After drying, the sludge would be placed on
local farm fields.
During the long-term evaluation phase of this project,
sludge samples were collected from three locations
within the sludge settling pond at Plant A. These sludge
samples were analyzed for pH, percent moisture, total
arsenic, total aluminum, total manganese, and total iron.
Also, a TCLP test was performed on each sample to
determine the quantities of leachable arsenic, barium,
cadmium, chromium, lead, mercury, selenium, and sil-
ver. Total arsenic concentrations ranged from 255 mg/kg
to 392 mg/kg, and total iron ranged from 78,600 mg/kg
to 93,000 mg/kg. Arsenic was detected at less than
0.05 mg/L in the TCLP extraction procedure. Also, con-
centrations were below the more stringent regulatory
levels in California for total arsenic. Table 4-7 presents
the results of sludge analysis at each of the three sam-
pling locations.
Table 4-6. Summary of Analytical Results from Supernatant Discharge Samples at Plant A
(November 11, 1998-June 16, 1999)
Parameter
As (total)
As (soluble)
As (particulate)
PH
Total Al
Total Fe
Total Mn
Dissolved Al
Dissolved Fe
Dissolved Mn
Units
ug/L
M9/L
ug/L
Mg/L
M9/L
M9/L
Mg/L
Mg/L
ug/L
Number of Sample
Events
8
8
8
8
8
8
8
8
8
8
Minimum
9.4
3.3
5.2
4.6
<11
1,048
101.5
<11
<30
16.5
Maximum
167.0
138.0
111.5
7.9
20.0
14,470
1746
<11
92.0
1020
Average
72.4
28.7
43.6
7.2
12.2
5,780
974
<11
<30
186.3
Stardard Deviation
59.4
46.3
34.9
1.1
5.0
4,527
666
NA
27.1
342
27
-------
Table 4-7. Analytical Results of Sludge Sampling at Plant A (November 18,1998)
Parameter
Unit
*D.L.
Location 1
Location 2
* Detection limit
(a) Re-analyzed by Wilson Environmental Laboratories.
Location 3
As-TCLP
Ba-TCLP
Cd-TCLP
Cr-TCLP
Pb-TCLP
Hg-TCLP
Se-TCLP
Ag-TCLP
Percent moisture
TCLP extraction
PH
Total As
Total Al
Total Fe
Total Mn
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
%
-
_
mg/kg, dry
mg/kg, dry
mg/kg, dry
mg/kg, dry
0.05
1.0
0.020
0.030
0.20
0.0002
0.05
0.020
0.1
<0.05
19.4
<0.020
<0.030
<0.20
<0.0002
<0.05
<0.02
40.5
complete
7.6
255""
7,300
78,600W
NA
<0.05
18.2
<0.020
0.040
<0.20
<0.0002
<0.05
<0.02
46.9
complete
7.6
392
5,000
89,070
1,490
<0.05
5.1
<0.020
<0.030
<0.20
<0.0002
<0.05
<0.02
46.1
complete
7.5
372
4,580
93,000
1,950
4.3 Plants
Source water sampling at Plant B was performed in Feb-
ruary 1998. Preliminary sampling consisted of weekly
water sampling for a four-week period in May 1998.
Long-term sampling was initiated in June 1998 and con-
tinued through December 1998. Arsenic speciation sam-
pling was conducted every fourth week. The third phase
of this study also included collection and analysis of recy-
cle supernatant during two sampling events in November
1998 and January 1999. No sludge samples were col-
lected at Plant B.
4.3.1 Plant B Description
Plant B began operation in the spring of 1993 and pro-
vides a portion of the treated water for approximately
6,000 residents and up to 20,000 tourists. The plant
utilizes an iron removal process for water treatment and
can process 1.4 mgd. The plant typically operates from
June through November. Figure 4-6 is a schematic dia-
gram of the treatment process at Plant A.
The treatment process at Plant B consists of the follow-
ing major elements:
• intake. The plant intake consists of water from a
mining tunnel and recycle supernatant from
backwashing activities.
• Chlorination. Approximately 3 mg/L
(37-40 Ib/day) of chlorine is added for iron
and manganese oxidation.
• Reaction Vessels. There are two reaction vessels
in series and sulfur dioxide (3-4 Ib/day) is added
after the first reaction vessel based on manufac-
turers recommendation to reduce polysulfide in the
filter media. These reaction vessels are designed
to handle 4,000 gallons per minute (gpm).
• Filtration Vessel. The filtration vessel contains
five layers of filtering media, including anthracite
coal. The filtering rate is 10 gpm/ft2, and the vessel
is backwashed every 8 hours or at 10 pounds per
square inch (psi) pressure differential.
• Blending. Treated water is blended with non-
treated water from another mining tunnel and one
spring in the finished water wet well. No post-
treatment chlorination is performed because the
residual chlorine is 1 to 2 mg/L.
• Backwash. Backwash water is sent to a concrete
vat where the solids are settled out and the super-
natant water is recycled after about 90 minutes of
settling. This water is sent back to the intake where
it is blended with the raw water from the mining
tunnel. The solids settle to the bottom of the
concrete vat and are then sent to a sludge holding
tank. This sludge is processed through a filter
press and then sent to a municipal landfill.
4.3.2 Initial Source Water Sampling
Source water at Plant B comes from surface water runoff
transported via a mining tunnel. Following treatment, this
source water is blended with several other sources,
including another mining tunnel, one spring, and three
deep wells. These other sources do not require treatment.
The blended water is chlorinated and distributed. Based
on discussions with plant personnel, the water treated at
Plant B has a turbidity of approximately 4-14 NTU and is
supplied at a flowrate of approximately 7.5 cubic feet per
second (cfs). Historically, arsenic concentrations in the
source water have ranged from 40 to 80 (ig/L.
28
-------
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An initial site visit to Plant B was conducted on February
4,1998, and source water samples were collected at that
time. During this sampling event, samples were collected
and analyzed for arsenic (total, particulate, soluble,
As[lll], and As[V]) and other water quality parameters that
may affect arsenic removal. Table 4-8 presents the ana-
lytical results from the source water sampling. The total
arsenic concentrations in the source water averaged
48.6 ug/L. Particulate arsenic averaged at 35.7 ug/L and
the soluble arsenic was mostly As(V), measured at
10.8 ug/L. The average As(lll) concentration measured dur-
ing the initial source water sampling event was 2.1 ug/L
Also, the inlet iron concentration averaged 890 ug/L, the
aluminum concentration was less than the detection limit,
and the average manganese concentration was 50 ug/L.
Alkalinity concentrations averaged 135 mg/L (as CaCO3)
and total hardness concentrations averaged 522.5 mg/L.
Therefore, the source water was considered very hard.
Turbidity averaged 4.0 NTU and the sulfate concentra-
tion averaged 420 mg/L. The pH averaged 7.7, which is
in the range where no effect on arsenic removal efficien-
cy using iron hydroxide precipitation has been observed
in previous studies (Sorg and Logsdon, 1978; Sorg, 1993;
Heringetal., 1996).
4.3.3 Preliminary Sampling
Water samples collected during the preliminary sampling
phase of this study were taken at three locations within
the treatment plant: the inlet to the plant (IN), before the
filtration process (PF), and after the filtration process
(AF). Sample taps were used to collect samples at each
location. The IN samples were collected at the influent of
the system after the source water was combined with the
recycle supernatant from the concrete vat. The PF
samples were collected after addition of chlorine and
processing of water through the two reaction vessels. AF
samples were collected immediately following filtration
and represent finished water. Figure 4-7 is a process
flow diagram for Plant B that shows sampling locations
used during the preliminary and long-term sampling, as
well as the analyses performed on samples collected
from each location.
Alkalinity, pH, total iron, total manganese, and total
arsenic analysis were performed on all water samples
collected at Plant B. Turbidity and hardness analysis and
arsenic speciation sampling were conducted at each
sampling location once during the preliminary study.
Arsenic form (soluble and particulate) and species (arse-
nate and arsenite) were determined as part of the arse-
nic speciation. Table 4-9 presents the results of the four-
week preliminary sampling period.
Results from the preliminary sampling events indicated
that inlet total arsenic concentrations ranged from 34.1 to
45.7 ug/L. The total arsenic in the source water was pri-
marily particulate and the soluble fraction of the total
arsenic was primarily As(V). The As(lll) concentrations
measured during the preliminary sampling period was
relatively low, averaging only 2.6 ug/L. As expected, the
species of arsenic did not vary significantly during the
treatment process. The average total arsenic removed
was approximately 64% during preliminary sampling,
leaving an average of 15.0 ug/L of total arsenic in the fin-
ished water. Arsenic speciation sampling during the first
week of the sampling period indicated that soluble arse-
nic was not removed and that only the arsenic entering
the treatment plant as particulate was removed. Because
Table 4-8. Source Water Analytical Results at Plant B (February 4,1998)
Parameter
Unit
Primary Sample
Duplicate Sample
Average Concentration
Alkalinity
Sulfate
Turbidity
pH
Hardness
Ca Hardness
Mg Hardness
Total Al
Total Fe
Total Mn
NOj-NO, (N)
TOG
As (total)
As (total soluble)
As (particulate)
As (III)
As(V)
mg/L"'
mg/L
NTU
—
mg/L"1
mg/L"1
mg/L"1
pg/L
ug/L
ug/L
mg/L°"
mg/L
ug/L
ug/L
pg/L
ug/L
Mg/L
134
420
4
7.7
537
402
135
<400
910
60
0.11
1
49.7
13.0
36.7
2.0
11.0
136
420
4.1
7.7
508
370
138
<400
870
40
0.11
1
47.6
12.8
34.8
2.3
10.5
135
420
4.0
7.7
522
.386
136
<400
890
50
0.11
1
48.6
12.9
35.7
2.1
10.8
(a) As CaCO,.
(b) Combined NO..-N and NOa-N.
30
-------
SLUDGE PROCESSED THROUGH A
FILTER PRESS AND SENT TO A
MUNICIPAL LANDFILL
SLUDGE HOLDING
TANK
CONCRETE VAT
MONTHLY
Dissolved and total As,
Al, Fe, and Mn; pH "^" ~
As (total), As (III), As (V),
Turbidity, Hardness, ^
Dissolved Al, Fe, and Mn
SO2*
As (total), As (III), As (V),
Turbidity, Hardness, -
Dissolved Al, Fe, and Mn
Backwash
water
As (total), As (III), As (V),
Turbidity, Hardness,
Dissolved Al, Fe, and Mn "*
INFLUENT
RECLAIMED
SUPERNATANT WATERl
: SO2 recommended by manufacturer to reduce
polysulfide formation on the filter media.
REACTION
VESSEL #1
REACTION
VESSEL #2
FILTRATION
VESSEL
DISTRIBUTION
SYSTEM
Plant B
Iron Removal
Design Flow: 1.4 mgd
WEEKLY
As (total), Alkalinity, pH,
Total Al, Fe, and Mn
As (total), Alkalinity, pH,
Total Al,Fe, and Mn
. w As (total), Alkalinity, pH,
Total Al, Fe, and Mn
LEGEND
SO,
Sampling Location
Disinfectant Addition
Point
Unit Process
Chemical Added to
Unit Process
Figure 4-7. Process Flow Diagram and Sampling Locations at Plant B
31
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of this, the simplified sorption model proposed by McNeill
and Edwards (1997) does not apply to the arsenic
removal results at this plant.
Other water quality parameters also were analyzed to
support understanding of mechanisms of arsenic re-
moval. Similar to Plant A, alkalinity concentrations and
pH decreased slightly between the IN and PF sampling
locations, due to the stoichiometry of iron oxidation in
which hydrogen ions are produced and alkalinity is
destroyed (Benefield and Morgan, 1990). As would be
expected, alkalinity and pH remained constant between
the PF and AF sampling locations. Source water turbidity
concentrations averaged 3.5 NTU, which was consistent
with plant data and data obtained during the initial
source water sampling. Unlike Plant A, increased tur-
bidity due to oxidation of iron after sample collection and
prior to analysis was not an issue at Plant B because the
iron entered the facility in oxidized form. Plant B effec-
tively removed turbidity with finished water concen-
trations averaging <0.1 NTU. Also, as observed during
the source water sampling event, the source water is
very hard. No removal of hardness by the treatment pro-
cess was observed during the preliminary sampling.
Total manganese concentrations were relatively low,
averaging 55 ug/L in the source water, 45 ug/L prior to
filtration, and <20 after filtration. Total iron concentra-
tions averaged 825 ug/L. in the source water, 884 ug/L
prior to filtration, and 75 ug/L after filtration. The inlet iron
concentrations were consistent with those observed dur-
ing the initial source water sampling event. It appeared
that arsenic removal was primarily achieved through
filtration of iron particles to which arsenic was sorbed
prior to treatment at Plant B.
Only minor changes were made to the approach for the
long-term evaluation as a result of the preliminary sam-
pling effort. As with Plant A, sampling locations and
primary analytes remained unchanged, except for the
addition of aluminum. Iron and manganese analysis
were modified to achieve lower detection limits by using
ICP-MS. Also, it was determined that part of the sample
in bottle B from the arsenic speciation kits would be used
to determined dissolved aluminum, iron, and manganese
concentrations.
4.3.4 Long-Term Sampling
Long-term sampling and analysis consisted of 26 weeks
of water sampling at the three locations used during the
preliminary sampling phase. All weekly samples were
analyzed for total arsenic, alkalinity, pH, total aluminum,
total iron, and total manganese. Turbidity, hardness, dis-
solved aluminum, dissolved iron, and dissolved manga-
nese analysis, as well as arsenic speciation sampling
were conducted at each sampling location'a total of
seven times during the long-term sampling phase. Arse-
nic speciation sampling included the determination of
soluble arsenic, particulate arsenic, As(V), and As(lll)
concentrations. Recycle supernatant discharge analysis
was performed twice during this phase. Sludge samples
were not collected at Plant B during this study; however,
results from sludge sampling conducted in 1994 are dis-
cussed in Subsection 4.3.4.4. The following subsections
summarize the arsenic, water quality parameter, and
residual analytical results.
4.3.4.1 Arsenic
Table 4-10 provides a summary of the arsenic analytical
results collected at the three sampling locations at Plant
B. Total arsenic concentrations at the inlet location
ranged from 33.3 to 97.9 ug/L, with an average con-
centration of 48.5 ug/L. Total arsenic concentrations at
the prefiltration location ranged from 6.7 to 81.1 ug/L
Table 4-10. Summary of Arsenic Analytical Results at Plant B (June 11, 1998-December 8, 1998)
Parameter
As (total)
As (total soluble)
As (particulate)
As (III)
As(V)
Sample
Location
Inlet
Prefiltration
After filtration
Inlet
Prefiltration
After filtration
Inlet
Prefiltration
After filtration
Inlet
Prefiltration
After filtration
Inlet
Prefiltration
After filtration
Units
Pg/L
Pg/L
Pg/L
Mg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
Mg/L
pg/L
pg/L
pg/L
pg/L
Number of
Samples
26
26
26
7
7
7
7
7
7
7
7
7
7
7
7
Minimum
33.3
6.7
5.3
4.9
0.8
5.3
20.9
17.9
<0.1
0.1
0.2
0.1
3.1
0.4
5.1
Maximum
97.9
81.1
19.7
15.7
14.4
20.1
70.0
65.8
3.1
2.2
0.8
0.8
15.0
14.0
19.8
Average
48.5
41.8
11.9
11.9
10.8
11.4
38.9
40.1
1.3
1.4
0.5
0.3
10.5
10.2
11.1
Standard
Deviation
16.3
16.6
3.3
3.7
4.7
4.4
18.3
18.0
1.4
0.82
0.21
0.28
3.9
4.7
4.4
33
-------
with an average of 41.8 ug/L. Therefore, very little arse-
nic was removed prior to filtration. Samples collected at
the AF location contained total arsenic concentrations
ranging from 5.3 to 19.7 ug/L, with an average of 11.9
ug/L. The average removal efficiency of total arsenic
(comparing raw water to finished water concentrations)
was 74%. Figure 4-8 is a graph showing the arsenic con-
centrations recorded at each sampling location through-
out the study.
Particulate arsenic concentrations averaged 38.9 ug/L at
the inlet, 40.1 ug/L prior to filtration, and 1.3 ug/L after
filtration. These results indicate that very little adsorption
and coprecipitation of soluble arsenic occurs during the
treatment process. Instead, the arsenic most likely is
attached to the oxidized iron particles prior to entering
the facility.
This observation is supported by the As(lll) and As(V)
analytical results. As(lll) and As(V) make up the soluble
fraction of the total arsenic concentration. As(lll) concen-
trations in the source water ranged from 0.1 to 2.2 ug/L,
with an average of 1.4 ug/L Some of the As(lll) was
converted to As(V) during chlorination, resulting in aver-
age As(lll) concentrations at the prefiltration and after-
filtration sampling locations of 0.5 ug/L and 0.3 ug/L,
respectively. As(V) concentrations averaged 10.5 ug/L at
the inlet, 10.2 ug/L prior to filtration, and 11.1 ug/L in the
finished water. It is interesting that very little soluble ar-
senic was removed at Plant B. This observation is most
likely a result of the lack of reduced iron in the source
water. Approximately 90% of the iron entering the facility
is in the oxidized form, to which arsenic has already
sorbed. Figure 4-9 provides charts showing the fractions
of the total arsenic concentration made up by particulate
arsenic and soluble arsenic [As(III) and As(V)].
The Plant B water treatment system only removed arse-
nic that entered the facility in particulate form. This arse-
nic was most likely already sorbed to the oxidized iron
entering the facility. Also, with an average finished water
total arsenic concentration of 11.9 ug/L, Plant B was not
able to consistently remove arsenic from source water to
low levels. However, arsenic removal would most likely
be enhanced if a coagulant such as ferric chloride was
included in the treatment process.
4.3.4.2 Other Water Quality Parameters
Table 4-11 summarizes the analytical results for several
water quality parameters obtained during long-term sam-
pling. Similar to that observed during the preliminary
study, alkalinity concentrations were relatively constant
throughout long-term sampling as well as throughout the
o%
5/25/98 6/24/98 7/24/98 8/23/98 9/22/98 10/22/98 11/21/98 12/21/98
Date
Figure 4-8. Total Arsenic Analytical Results During Long-Term Sampling at Plant B
34
-------
Inlet
o
O
90-T
80 -
70-
60 •
50 -
40 -
30-
20 -
10-
0-
* _o?>
dS»° oP
$° .&
** /-
' ^
90
Prefiltration
80 -
70
60 •
40 •
30 -
20
10 -
0
After Filtration
i
90
80
70 -
60 •
50
40
30 •
20 •
10 -
0
Figure 4-9. Arsenic Form and Species Analytical Results During Long-Term Sampling at Plant B
35
-------
Table 4-11. Summary of Water Quality Parameter Analytical Results at Plant B (June 11,1998-December 8,1998)
Parameter
Alkalinity
Turbidity
PH
Total Hardness
Total Al
Total Fe
Total Mn
Dissolved Al
Dissolved Fe
Dissolved Mn
Sample
Location
Inlet
Prefiltration
After filtration
Inlet
Prefiltration
After filtration
Inlet
Prefiltration
After filtration
Inlet
Prefiltration
After filtration
Inlet
Prefiltration
After filtration
Inlet
Prefiltration
After filtration
Inlet
Prefiltration
After filtration
Inlet
Prefiltration
After filtration
Inlet
Prefiltration
After filtration
Inlet
Prefiltration
After filtration
Units
mg/L
mg/L
mg/L
NTU
NTU
NTU
_
_
—
mg/L
mg/L
mg/L
Pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
pg/L
N umber of
Samples
26
26
26
7
7
7
26
26
26
7
7
7
26
26
26
26
26
26
26
26
26
7
7
7
7
7
7
7
7
7
Minimum
137
133
132
4.6
4.0
0.2
7.5
7.2
7.5
377
329
359
<11
<11
<11
599
116
<30
29.9
13.8
<0.5
<11
<11
<11
<30
<30
<30
25
9.4
<0.5
Maximum
145
143
142
13.3
13.1
0.8
8.6
7.9
7.8
494
473
482
46.9
47.8
36.8
2,753
2,167
306
135
151
9.1
<11
<11
<11
655
44.4
31.5
41.1
30.2
0.9
Average
140
137
137
8.8
8.0
0.4
7.9
7.7
7.7
443
.421
420
22.0
22.1
13.9
1,137
1,001
66.7
61.6
50.3
1.9
<11
<11
<11
107
<30
<30
31.9
25.1
<0.5
Standard
Deviation
2.2
2.6
2.6
3.5
, 3.6
0.22
0.20
0.14
0.08
42.9
52.4
46.6
10.7
11.1
8.0
598
509
60.8
27.0
27.3
2.1
NA
NA
NA
242
11.1
6.2
4.9
7.1
0.30
treatment process, with only a slight decrease in concen-
tration between samples collected at the inlet and prefil-
tration sampling locations. Figure 4-10 shows source
water alkalinity, turbidity, pH, and hardness concentra-
tions throughout the long-term sampling phase. Average
alkalinity concentrations at the inlet, prefiltration, and after-
filtration sampling locations were 140 mg/L, 137 mg/L,
and 137 mg/L (as CaCOS), respectively. Because the iron
entered the facility already oxidized, there was very little
alkalinity reduction following chlorination.
During the long-term sampling, turbidity concentrations
averaged 8.8 NTU at the inlet, 8.0 NTU at the PF loca-
tion, and 0.4 NTU in the finished water, which are con-
sistent with plant data. As shown in Figure 4-10, source
water turbidity concentrations fluctuated significantly.
These fluctuations would be expected for a surface water
source and are probably a result of precipitation events
and/or snowmelt. The plant was effective at removing
turbidity. Hardness was not significantly removed by the
treatment process. Average hardness concentrations in
samples collected at the plant inlet, before filtration, and
after filtration were measured at 443 mg/L, 421 mg/L,
and 420 mg/L, respectively. As shown in Figure 4-10,
source water hardness appears to increase throughout
the study, although the reason for this is not clear.
Values for pH were relatively .constant throughout the
duration of the study and throughout the treatment pro-
cess. Average pH was 7.9 in the source water, 7.7 prior
to filtration, and 7.7 after filtration.
Total aluminum concentrations at the IN and PF sam-
pling locations averaged approximately 22.0 u.g/L and
decreased in the AF samples to 13.9 ug/L. The majority
of the aluminum detected in water samples from the inlet
sampling location was particulate form. The dissolved
aluminum concentration was <11 ug/L throughout the
study at each sampling location. Due to the relatively low
total aluminum concentrations, aluminum is not believed
to have a significant effect on arsenic removal.
Total manganese concentrations averaged 61.6 ug/L,
50.3 ug/L, and 1.9 ug/L in samples collected at the inlet,
prefiltration, and after-filtration sampling locations, respec-
tively. Average dissolved manganese concentrations were
31.9 ug/L in the source water, 25.1 ug/L before filtration,
and <0.5 ug/L after filtration. Previous studies have not
correlated manganese removal to arsenic removal; there-
fore, manganese is not believed to have a significant
impact on arsenic removal efficiency.
36
-------
20
16
14
s
I 12
10 -
8 .
6 .
2 .
600
- 500
- -400
Turbidity (NTU)
pH (units)
Hardness (mg/L as CaCOj)
Alkalinity (n#L as CaCQj)
- .200
-. 100
5/2398 6/24/98
7/24/98
8/23/98 9/22/98
Date
10/22/98
11/21/98
12/21/98
Figure 4-10. Inlet Turbidity, pH, Hardness, and Alkalinity Analytical Results at Plant B
Total iron concentrations in samples collected at the IN
sampling location ranged from 599 to 2,753 ug/L, with an
average of 1,137 ug/L. At the PF sampling location, total
iron concentrations ranged from 116 to 2,167 ug/L, with
an average of 1,001 ug/L. The average iron concen-
tration in samples collected after filtration was 66.7 ug/L.
Also, dissolved iron concentrations were relatively low in
the source water, averaging 107 ug/L. All dissolved iron
was oxidized during chlorination prior to filtration, result-
ing in average dissolved iron concentrations of <30 ug/L
in samples collected at the prefiltration and after-filtration
sampling locations. As stated previously, it is believed that
arsenic removal at Plant B is achieved primarily through
filtration of arsenic sorbed to iron particles formed prior to
entering the facility.
4.3.4.3 Recycle Supernatant
The filtered backwash water is sent to a concrete vat,
where it is given time to settle. The supernatant water
then is recycled to the inlet of the plant and mixed with
the source water from the mining tunnel. On November
10, 1998 and January 15, 1999, supernatant samples
were collected to determine the concentrations of arse-
nic, aluminum, iron, and manganese recycled to the sys-
tem. The November 10 test results show that essentially
all of the arsenic (142 ug/L average) in the recycle
supernatant water was in particulate form. In contrast,
the arsenic results from January 15, 1999 were signifi-
cantly lower (7.8 ^ig/L). This lower level most likely is
because the plant did not operate in January 1999, there-
by giving the backwash water in the concrete vat more
time to settle. During typical operations, as observed in
November 1998, the supernatant from the concrete vat
is recycled every 90 minutes. The results for aluminum,
iron, and manganese were significantly less on January
15, 1999 than on November 10, 1998, which is consist-
ent with the results observed for arsenic. The recycled
backwash water sample analytical results are shown in
Table 4-12.
4.3.4.4 Sludge
Sludge is generated at Plant B from filter backwashing.
Sludge that settles in the concrete vat is transferred to a
sludge holding tank. Approximately once a year, sludge is
removed from the sludge holding tank, processed through
a filter press, and sent to a municipal landfill. Based on
discussions with plant personnel, approximately 2 to 3 yd3
of dewatered sludge is sent to a nonhazardous landfill
every year. Sludge samples were not collected at Plant B
as part of this study; however, the plant provided results
from a sludge sampling event conducted in January 1994.
A primary compound detected in the sludge was Fe2O3,
which comprised 30.4% by weight. Arsenic was detected
at 6,700 mg/kg in the sludge sample.
37
-------
Table 4-12. Summary of Analytical Results from Recycle Supernatant Samples at Plant B
Parameter
Unit
11/10/98
01/15/99
pH
As (total)
As (total soluble)
As (paniculate)
Total Al
Total Fe
Total Mn
Dissolved Al
Dissolved Fe
Dissolved Mn
ug/t
7.8
7.8
146
138
5.3
4.8
141
133
58.2
51.5
3,850
3,710
326
267
30.4
31.1
<30
<30
1.0
1.0
8.1
8.1
7.8
7.8
7.7
7.8
75.2
67.4
1.6
1.7
<30
<30
<0.5
<0.5
38
-------
5.0 Quality Assurance/Quality Control
5.1 Quality Assurance Objectives
The precision, accuracy, MDL, and completeness for
each of the analytical measurements required for this
study have been established in the QAPP (Battelle,
1998) and are listed in Table 1 of the Quality Assurance/
Quality Control (QA/QC) Summary Report (Battelle,
2000), which was prepared under separate cover. These
terms serve as indicators of data quality and were
calculated in accordance with the formulas provided in
the QAPP. The precision, accuracy, and MDL of each of
the measurements performed during the present study
are presented in the summary report. These quality
assurance (QA) data are organized according to the
date of sample receipt or sample analysis and are not
site-specific. Therefore, the QA/QC section of this report
shares the same QA data with other water treatment
plants that have been included in the study.
5.2 Overall Assessment of Data Quality
Quantitative QA objectives listed in the QA/QC Summary
Report include precision as relative percent difference
(RPD), accuracy as percent recovery (%R), MDL, and
completeness. The precision, accuracy, and MDL or re-
porting limit of each of the measurements performed
during the present study are presented in the QA/QC
Summary Report. Total arsenic, aluminum, iron, and
manganese analyses on water samples were conducted
in Battelle's ICP-MS laboratory. The QA data associated
with these metal analyses also are presented in the
QA/QC Summary Report. Other water quality param-
eters including alkalinity, pH, turbidity, hardness, nitrate-
nitrite, sulfate, fluoride, total dissolved solids (TDS), and
TSS were analyzed by Wilson Environmental Labor-
atories and their QA data are summarized in the QA/QC
Summary Report. QA data for TOC analysis performed
by CT&E Environmental Laboratory are presented in the
QA/QC Summary Report. The TCLP metal analysis on
sludge samples also was conducted by Wilson Envi-
ronmental Laboratories and its associated QA data are
summarized. Overall, the QA objectives of precision,
accuracy, MDL, and completeness were achieved by all
laboratories. Therefore, all the valid data were used to
evaluate the effectiveness of the treatment processes
and support conclusions.
5.2.1 Total Arsenic, Aluminum, Iron,
and Manganese
At the early phase of the study, total arsenic analysis
was performed by Battelle's ICP-MS laboratory, and total
Al, Fe, and Mn were analyzed by Wilson Environmental
Laboratories. Starting from June 1998, all four metals
were analyzed by Battelle ICP-MS laboratory. Therefore,
QA data for only the total arsenic analysis before June
16, 1998 and QA data for all four metals afterwards are
presented.
The laboratory duplicate and matrix spike analyses were
performed every 10 samples instead of 20 samples as
required by the QAPP. All the samples were analyzed
for four metals although metals other than arsenic may
not be required for every sample. Therefore, Battelle's
ICP-MS laboratory performed more QA/QC analyses
than what were specified in the QAPP. This fact should
be considered when QC data are evaluated.
Greater than 99% of the precision results for all metals
met the QA objective of ±25% (with only two Fe outliers:
27% on August 8, 1998 and 74% on December 22,
1998; three As outliers: 27% on August 18, 1998, 182%
on October 1, 1998, and 27% on July 30, 1999; and four
Al outliers: 26% and 33% on August 18, 1998, 48% on
December 15, 1998, and 48% on January 25, 1999).
The majority of the accuracy data associated with matrix
spike (MS) analysis on August 31, 1998 exceeded the QA
limits of 75 to 125%. It is suspected that matrix spike
analyses were not performed correctly on that day. After
this problem had been identified, Battelle's Work Assign-
ment Leader, laboratory QA officer, and Battelle's task
leaders met to discuss the cause of the deviation. Correc-
tive actions were taken including re-analyzing samples
and adjusting the amount of spike added to samples (i.e.,
39
-------
the Fe spike was increased from 50 to 100, 200, 225, or
even as high as 2,000 ug/L because most of samples
contain much more than 50 ug/L of Fe). As indicated in
the QA/QC Summary Report (Battelle, 2000), the matrix
spike data quality was significantly improved since
November 3, 1998. Excluding the data on August 31,
1998, only five As data were outside the acceptable
range for accuracy. However, 15 Al, 26 Fe, and 14 Mn
accuracy data did not meet the QA objective. With
exceptions of one 23% and one 38% of accuracy, the Al
accuracy data range from 65 to 125%. The Mn accuracy
data range from 67 to 106% with exception of one 37%.
The Fe accuracy data range from 55 to 142% with excep-
tions of one 14%, one 23%, and one 38%.
All laboratory control samples showed %R within the
acceptable QA limit of 75 to 125% except for six outliers
for total Fe with %R ranging from 73 to 143%. Al was not
spiked to laboratory control samples until November 3,
1998 after corrective actions were taken. The MDL of Fe
is the same as target MDL; however, MDLs of other
three metals were far below the target levels as specified
in the QAPP.
5.2.2 Water Quality Parameters
Water quality parameters include alkalinity, pH, turbidity,
hardness (Ca and Mg), nitrate-nitrite, sulfate, fluoride,
TDS, TSS and TOG. As shown in Table 3 of the QA/QC
Summary Report, all the precision data were within the
acceptable QA limit of ±25% except for two Mn analyses
with a 29% RPD (April 10 and 17, 1998) and three
nitrate-nitrite analyses with 40% RPD (August 6, 1998,
January 13, 1999, and February 11, 1999). The high
RPDs of these analyses might have caused by the low
measured concentrations in the samples that were close
to the detection limits for Mn and nitrate-nitrite. The ac-
curacy data indicate that only one Al (70% on March 2,
1998), two Mn (66% and 64% on May 12, 1998), and
one Mg (126% on August 7, 1998) %R slightly exceeded
the QA objectives of 75 to 125%. Although the matrix
spike duplicate (MSD) analysis was not required by the
QAPP, the accuracy and the precision data relating to
MSD also were presented. The MS/MSD analyses are not
applicable to pH and turbidity measurements, though. The
laboratory did not perform MS/MSD analyses on Ca and
Mg hardness analyses until October 15, 1998 at Battelle's
request. All laboratory control samples showed %R
within the acceptable QA limit of 75 to 125%. Reporting
limits were below the required levels for all the analytes
except for sulfate. The reporting limits of sulfate was
5 mg/L, exceeding the required MDL of 3.66 mg/L. All
precision, accuracy, and %R values for the TOG analy-
sis were within acceptable QA limits with the exception
of one accuracy value that was slightly below the 75 to
125% range at 72% (February 21,1999).
5.2.3 TCLP Metals in Sludge
The TCLP metals analyzed in the sludge samples in-
cluded As, Se, Hg, Ba, Cd, Cr, Pb, and Ag. The precision
data were within QA limits of ±25%. The accuracy of
matrix spikes and percent recovery of laboratory control
samples were all within QA limits of 75 to 125% except
for one slightly elevated RPD for TCLP Se MS/MSD at
26% (November 17,1998).
40
-------
6.0 References
Andreae, M. 1977. "Determination of Arsenic Species in
Natural Waters." Anal. Chem., 49: 820-823.
Battelle. 1998. Quality Assurance Project Plan for Evalu-
ation of Treatment Technology for the Removal of
Arsenic from Drinking Water. Prepared for EPA.
Battelle. 2000. Quality Assurance/Quality Control (QA/
QC) Summary Report for Evaluation of Treatment
Technologies for the Removal of Arsenic from Drinking
Water. Under preparation.
Benefield, L.D. and U.S. Morgan. 1990. "Chemical Pre-
cipitation." Water Quality and Treatment.
Chen, S.L., S.R. Dzeng, M. Yang, K. Chiu, G. Shieh, and
C.M. Wai. 1994. "Arsenic Species in Groundwaters of
the Blackfoot Disease Area, Taiwan." Environmental
Science and Technology. 877-881.
Cheng, R.C., S. Liang, H.C. Wang, and M.D. Beuhler.
1994. "Enhanced Coagulation for Arsenic Removal."
J. AWWA (September): 79-90.
Clifford, D., L. Ceber, and S. Chow. 1983. "Arsenic(lll)/
Arsenic(V) Separation by Chloride-Form Ion-Exchange
Resins." Proceedings of the XI AWWA WQTC.
Eaton, A.D., H.C. Wang, and J. Northington. 1997.
"Analytical Chemistry of Arsenic in Drinking Water."
AWWARF Project 914.
Edwards, M. 1994. "Chemistry of Arsenic Removal
during Coagulation and Fe-Mn Oxidation." J. AWWA
(September): 64-78.
Edwards, M., S. Patel, L. McNeill, H. Chen, M. Frey,
A.D. Eaton, R.C. Antweiler, and H.E. Taylor. 1998.
"Considerations in As Analysis and Speciation." J.
AWWA (March): 103-113.
EPA, see U.S. Environmental Protection Agency.
Ficklin, W.H. 1982. "Separation of Arsenic (III) and Ar-
senic (V) in Groundwaters by Ion Exchange." Talanta,
30(5): 371 -373.
Gulledge, J.H. and J.T. O'Conner. 1973. "Removal of
Arsenic (V) from Water by Adorption on Aluminum and
Ferric Hydroxides." J. AWWA (August): 548-552.
Hemond, H.F. 1995. "Movement and Distribution of
Arsenic in the Aberjona Watershed." Environmental
Health Perspectives.
Hering, J.G., P.Y. Chen, J.A. Wilkie, M. Elimelech, and
S. Lung. 1996. "Arsenic Removal by Ferric Chloride."
J.AWWA. (April): 155-167.
McNeill, L.S. and M. Edwards. 1995. "Soluble Arsenic
Removal at Water Treatment Plants." J. AWWA.
(April): 105-113.
McNeill, L.S. and M. Edwards. 1997. "Predicting As
Removal During Metal Hydroxide Precipitation." J.
AWWA. (January): 75-86.
Meng, X., S. Bang, and G.P. Korfiatis. 2000. "Effects of
Silicate, Sulfate, and Carbonate on Arsenic Removal
by Ferric Chloride." Water Resources, 34(4): 1255-
1261.
Sorg, T.J. 1993. "Removal of Arsenic From Drinking
Water by Conventional Treatment Methods." Proceed-
ings of the 1993 AWWA WQTC.
Sorg, T.J. and G.S. Logsdon. 1978. 'Treatment Tech-
nology to Meet the Interim Primary Drinking Water
Regulations for Inorganics: Part 2." J. AWWA (July).
Tate, C.H. and K.F. Arnold. 1990. "Health and Aesthetic
Aspects of Water Quality." In American Water Works
Association (Eds.), Water Quality and Treatment: A
Handbook of Community Water Supplies. New York:
McGraw-Hill.
41
-------
U.S. Environmental Protection Agency. 1998. Research
Plan for Arsenic in Drinking Water. EPA/600/4-98/042.
Office of Research and Development, Washington,
DC. February.
42
-------
APPENDIX A
Complete Analytical Results from Long-term Sampling at Plant A
43
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APPENDIX B
Complete Analytical Results from Long-Term Sampling at Plant B
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*U.S. GOVERNMENT PRINTING OFnCE: 2000-651-085/40903
-------
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United States
Environmental Protection Agency
National Risk Management
Research Laboratory, G-72
Cincinnati, OH 45268
Please make all necessary changes on the below label,
detach or copy, and return to the address in the upper
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